抗菌肽基因及研究進(jìn)展

./抗菌肽基因及研究進(jìn)展摘要抗菌肽是昆蟲先天性免疫系統(tǒng)中十分重要的效應(yīng)因子,近年來一直是昆蟲免疫學(xué)研究的熱點(diǎn)。家蠶作為鱗翅目昆蟲的代表,其抗菌肽研究取得了長足進(jìn)展。根據(jù)過去研究獲得的抗菌肽基因,并利用這些序列在家蠶基因組中進(jìn)行同源搜尋,共發(fā)現(xiàn)了40個家蠶抗菌肽基因。這些基因編碼的多肽在大小、氨基酸組成和性質(zhì)上差異很大,但基于結(jié)構(gòu)性質(zhì)可以分成3類：<1>具有α-螺旋結(jié)構(gòu)并且缺乏半胱氨酸<Cysteine,Cys>的線性抗菌肽；<2>富含脯氨酸和/或甘氨酸的抗菌肽;<3>富含半胱氨酸的環(huán)形抗菌肽。本文將以這3類結(jié)構(gòu)作為主線綜述家蠶抗菌肽近年來的研究進(jìn)展。關(guān)鍵詞家蠶；抗菌肽；結(jié)構(gòu)AntimicrobialPeptideGenesinBombyxmoriandTheirResearchProgressSUNWei1,SHENYihong1,XIANGZhonghuai1,ZHANGZe1,2〔1.ThekeySericulturalLaboratoryofAgriculturalMinistry,SouthwestUniversity,Chongqing400716,China.2.TheInstituteofAgriculturalandLifeSciences,Chongqing400030,ChinaAbstractAntimicrobialpeptidesaretheimportanteffectorsoftheinnateimmunesystemininsects,whicharealwaysthehotresearchoftheinsectimmune.SilkwormistherepresentativeoftheLepidoptera,andtheresearchesofantimicrobialpeptidesinsilkwormmakeagreatprogress.AlocalBLASTsearchofthesilkwormgenomedatabaseidentified40antimicrobialpeptidegenes.Thoughthepeptidesencodedbythesegeneshavegreatdifferencesinsize,aminoacidcompositionandproperties,theycouldbegroupedinto3categories:<1>linearpeptidesformingα-helicesandwithoutcysteineresidues;<2>cyclicpeptidescontainingcysteineresidues;<3>peptideswithanoverrepresentationinprolineand/orglycineresidues.Thereviewpresentsthemainresearchesinthefieldofantimicrobialpeptidesfromsilkwormwiththesethreeaspectsduringtheseyears.KeywordsBombyxmori;antimicrobialpeptides;structure昆蟲是一類進(jìn)化上較為低等的動物,同時也是世界上種類和數(shù)量最多的動物。面對大量的外源微生物的侵害,雖然沒有類似于哺乳動物的特異性免疫系統(tǒng),但是仍然能夠較好的生存,說明昆蟲必定有對非特異因子產(chǎn)生免疫應(yīng)答的高效先天免疫系統(tǒng)。昆蟲的免疫系統(tǒng)由體液免疫和細(xì)胞免疫組成。細(xì)胞免疫主要是血細(xì)胞吞噬和消化外來異物,與高等動物類似。黑化反應(yīng)也是昆蟲重要的細(xì)胞免疫,血淋巴和血細(xì)胞中,當(dāng)外源物侵入昆蟲血腔時,激發(fā)了絲氨酸蛋白酶的級聯(lián)反應(yīng)形成黑色素。這樣,當(dāng)酚氧化酶沉積在外源微生物表面時,可形成能阻止其生長和運(yùn)動并且將其與寄主組織隔離的黑化包囊ADDINEN.CITE<EndNote><Cite><Author>Kimbrell</Author><Year>2001</Year><RecNum>79</RecNum><record><rec-number>79</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Kimbrell,D.A.</author><author>Beutler,B.</author></authors></contributors><auth-address>DepartmentofMolecularandCellularBiology,UniversityofCalifornia,1ShieldsAvenue,Davis,California95616-8535,USA.dakimbrell@</auth-address><titles><title>Theevolutionandgeneticsofinnateimmunity</title><secondary-title>NatRevGenet</secondary-title></titles><periodical><full-title>NatRevGenet</full-title></periodical><pages>256-67</pages><volume>2</volume><number>4</number><keywords><keyword>Animals</keyword><keyword>Apoptosis</keyword><keyword>Drosophila/genetics/*immunology/microbiology</keyword><keyword>*DrosophilaProteins</keyword><keyword>*Evolution</keyword><keyword>Humans</keyword><keyword>Immunity,Natural/*genetics/*immunology</keyword><keyword>Infection/immunology</keyword><keyword>InsectProteins/genetics/*immunology</keyword><keyword>Interleukin-1/chemistry/genetics/immunology</keyword><keyword>MembraneGlycoproteins/genetics/*immunology</keyword><keyword>Phylogeny</keyword><keyword>Receptors,CellSurface/genetics/immunology</keyword><keyword>SignalTransduction</keyword><keyword>Toll-LikeReceptor5</keyword><keyword>Toll-LikeReceptors</keyword></keywords><dates><year>2001</year><pub-dates><date>Apr</date></pub-dates></dates><accession-num>11283698</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11283698</url></related-urls></urls></record></Cite></EndNote>[1]。由于沒有抗體和補(bǔ)體系統(tǒng),昆蟲的體液免疫與高等動物有明顯差異,主要依賴血液中的抗菌肽和蛋白質(zhì)ADDINEN.CITE<EndNote><Cite><Author>Kimbrell</Author><Year>2001</Year><RecNum>79</RecNum><record><rec-number>79</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Kimbrell,D.A.</author><author>Beutler,B.</author></authors></contributors><auth-address>DepartmentofMolecularandCellularBiology,UniversityofCalifornia,1ShieldsAvenue,Davis,California95616-8535,USA.dakimbrell@</auth-address><titles><title>Theevolutionandgeneticsofinnateimmunity</title><secondary-title>NatRevGenet</secondary-title></titles><periodical><full-title>NatRevGenet</full-title></periodical><pages>256-67</pages><volume>2</volume><number>4</number><keywords><keyword>Animals</keyword><keyword>Apoptosis</keyword><keyword>Drosophila/genetics/*immunology/microbiology</keyword><keyword>*DrosophilaProteins</keyword><keyword>*Evolution</keyword><keyword>Humans</keyword><keyword>Immunity,Natural/*genetics/*immunology</keyword><keyword>Infection/immunology</keyword><keyword>InsectProteins/genetics/*immunology</keyword><keyword>Interleukin-1/chemistry/genetics/immunology</keyword><keyword>MembraneGlycoproteins/genetics/*immunology</keyword><keyword>Phylogeny</keyword><keyword>Receptors,CellSurface/genetics/immunology</keyword><keyword>SignalTransduction</keyword><keyword>Toll-LikeReceptor5</keyword><keyword>Toll-LikeReceptors</keyword></keywords><dates><year>2001</year><pub-dates><date>Apr</date></pub-dates></dates><accession-num>11283698</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11283698</url></related-urls></urls></record></Cite></EndNote>[2]。當(dāng)昆蟲機(jī)體受到病原微生物侵染時,體內(nèi)的識別蛋白能夠識別微生物表面的肽聚糖或脂多糖或者其他物質(zhì),引發(fā)絲氨酸蛋白酶和解除絲氨酸蛋白酶抑制劑的細(xì)胞外級聯(lián)反應(yīng),激活細(xì)胞內(nèi)信號轉(zhuǎn)導(dǎo)途徑,最終在其脂肪體、血液、中腸和表皮等器官或組織中誘導(dǎo)產(chǎn)生抗菌肽〔Antimicrobialpeptides,AMPs,進(jìn)而殺滅外源微生物ADDINEN.CITE<EndNote><Cite><Author>Kimbrell</Author><Year>2001</Year><RecNum>79</RecNum><record><rec-number>79</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Kimbrell,D.A.</author><author>Beutler,B.</author></authors></contributors><auth-address>DepartmentofMolecularandCellularBiology,UniversityofCalifornia,1ShieldsAvenue,Davis,California95616-8535,USA.dakimbrell@</auth-address><titles><title>Theevolutionandgeneticsofinnateimmunity</title><secondary-title>NatRevGenet</secondary-title></titles><periodical><full-title>NatRevGenet</full-title></periodical><pages>256-67</pages><volume>2</volume><number>4</number><keywords><keyword>Animals</keyword><keyword>Apoptosis</keyword><keyword>Drosophila/genetics/*immunology/microbiology</keyword><keyword>*DrosophilaProteins</keyword><keyword>*Evolution</keyword><keyword>Humans</keyword><keyword>Immunity,Natural/*genetics/*immunology</keyword><keyword>Infection/immunology</keyword><keyword>InsectProteins/genetics/*immunology</keyword><keyword>Interleukin-1/chemistry/genetics/immunology</keyword><keyword>MembraneGlycoproteins/genetics/*immunology</keyword><keyword>Phylogeny</keyword><keyword>Receptors,CellSurface/genetics/immunology</keyword><keyword>SignalTransduction</keyword><keyword>Toll-LikeReceptor5</keyword><keyword>Toll-LikeReceptors</keyword></keywords><dates><year>2001</year><pub-dates><date>Apr</date></pub-dates></dates><accession-num>11283698</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11283698</url></related-urls></urls></record></Cite></EndNote>[1]?？咕?lt;AMPs>是一類普遍存在的防御性蛋白質(zhì),具有分子量小、理化性能穩(wěn)定和廣譜抗菌等特點(diǎn),在昆蟲先天免疫防御系統(tǒng)中起著重要的作用。昆蟲抗菌肽常以家族的形式存在,家族內(nèi)成員間的氨基酸相似性較大,編碼AMPs的基因通常以串聯(lián)重復(fù)的形式存在在同一條染色體上。目前對黑腹果蠅〔Drosophilamelanogaster抗菌肽的研究較為系統(tǒng),黑腹果蠅中共有21個抗菌肽,按其序列相似性和功能性質(zhì)可以分為7類ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><authov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[3]。但根據(jù)肽鏈的結(jié)構(gòu)特點(diǎn),昆蟲抗菌肽又可以分為三類ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[4]：具有α-螺旋結(jié)構(gòu)并且缺乏半胱氨酸<Cysteine,Cys>的線性抗菌肽；富含脯氨酸和/或甘氨酸的抗菌肽；富含半胱氨酸的環(huán)形抗菌肽。下面我們將以肽鏈結(jié)構(gòu)分類體系介紹家蠶抗菌肽基因及其研究進(jìn)展。1家蠶抗菌肽條目早在20XX,Cheng等人通過對家蠶基因組框架圖序列的找到了35條抗菌肽基因序列ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[6]。隨著研究的深入以及家蠶基因組精細(xì)圖的最近繪制完成,我們應(yīng)用相同的方法重新搜尋了新組裝的家蠶基因組,并新找到一個cecropin基因,加上近期Wen等人〔2008研究發(fā)現(xiàn)的defensinAADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[7],以及Kaneko等人〔2008獲得的defensinBADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[8],家蠶共有40個抗菌肽基因<表1>。數(shù)量上遠(yuǎn)比其它已測序完成的模式昆蟲—黑腹果蠅〔21個,岡比亞按蚊〔10個ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[9]和蜜蜂〔6個ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[10]多。不同昆蟲所含有的抗菌肽數(shù)目差異可能與這些物種的生活習(xí)性,棲居的環(huán)境的差異有關(guān)系。表1家蠶的抗菌肽Table1AntimicrobialpeptidesinBombyxmori抗菌肽名稱基因名稱基因數(shù)目有完整ORF的基因數(shù)目抗菌活性AttacinBmatt32抗革蘭氏陰性菌CecropinBmcec1212抗革蘭氏陽性菌,革蘭氏陰性菌和真菌EnbocinBmenb22抗革蘭氏陽性菌,革蘭氏陰性菌GloverinBmglv74抗革蘭氏陰性菌LebocinBmleb21抗革蘭氏陽性菌,革蘭氏陰性菌MoricinBmmor1212抗革蘭氏陽性菌,革蘭氏陰性菌DefensinBmdef22抗革蘭氏陽性菌,革蘭氏陰性菌總數(shù)40352線性的具有α-螺旋的抗菌肽具有α-螺旋的線性抗菌肽是一類數(shù)量較多、分布較廣的抗菌肽,從低等的節(jié)肢動物到高等的哺乳動物中都有存在,這類抗菌肽常具有兩類特征：是陽離子性質(zhì)的肽；活性結(jié)構(gòu)具有兩親性質(zhì),具有幾乎等量的極性氨基酸與非極性氨基酸的兩親性的α-螺旋對于穩(wěn)定抗菌肽結(jié)構(gòu)是十分重要的。第一個發(fā)現(xiàn)的α-螺旋抗菌肽是鱗翅目昆蟲惜古比天蠶〔Hyatophoracecropia的CecropinADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[11]。家蠶中屬于這種類型的抗菌肽有Cecropin、Moricin和Enbocin等三種。2.1Cecropins家族和Enbocin家族家蠶的Cecropins是一類短多肽,對革蘭氏陰性菌有強(qiáng)的抗菌活性,對革氏陽性菌的抗性較弱。自從在惜古比天蠶發(fā)現(xiàn)Cecropin以來,在鱗翅目及雙翅目昆蟲中又陸續(xù)發(fā)現(xiàn)了至少60種Cecropin類抗菌肽。圖1Cecropin家族和Ebocin家族以及Attacin家族抗菌肽基因在染色體上的位置。A:抗菌肽cecropin基因B-亞族,C-亞族,D-亞族和E-亞族基因以及Ebocin家族基因在第26號染色體上的位置；B:抗菌肽cecropin基因A-亞族基因BmcecA2和Attacin家族基因在第6號染色體上的位置。BmcecA1基因未能定位在染色體上。箭頭符號代表抗菌肽基因的可能的轉(zhuǎn)錄方向。Fig1ThechromosomelocationsofCecropin,EbocinandAttacingenes.A:ThelocationofCecropingenes<BmcecBs,BmcecC,BmcecDsandBmcecE>andEbocingenesonthe26thchromosome.B:ThelocationofCecropingenes<BmcecA>andAttacinsgenesonthe6thchromosome.BmcecA1cannotbelocatedonanychromosomes.Andthearrowsrepresenttheputativetranscriptorientationoftheantimicrobialpeptides.家蠶Cecropins是一個較大的家族,共有11個成員ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Trve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[6],按照它們的序列相似性分為5個亞簇—BmcecA<BmcecA1-BmcecA4>,BmcecB<BmcecB1-BmcecB5>,BmcecC<BmcecC>,BmcecD<BmcecD1-BmcecD2>和BmcecE<BmcecE>,除BmcecA外,其它9個Cecropins成員在家蠶基因組上串聯(lián)存在<圖1>。家蠶Cecropins由61-65個氨基酸組成,大多數(shù)沒有半胱氨酸,有兩個α-螺旋結(jié)構(gòu),如圖2所示,N-末端富含堿性氨基酸,C-末端富含疏水的氨基酸,并且在C-末端有酰胺化修飾,以此來增加Cecropin的穩(wěn)定性以及正電荷,從而提高抗菌效率ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[12]。BmcecA1和A2,BmcecB1和B2,BmcecD以及BmcecE等6個已有研究,當(dāng)受到免疫誘導(dǎo)時,這些基因均有明顯的表達(dá)上調(diào),而在正常狀態(tài)下,BmcecE與另外幾個基因的表達(dá)情況有顯著的差異ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[13],胚胎發(fā)育時期,只有BmcecE在的胚帶分化時有一個表達(dá)峰,其他的基因無；在幼蟲期該7個基因有極少量或沒有表達(dá)；在蛹期,只有BmcecE在腸內(nèi)有表達(dá),這些說明BmcecE可能在胚胎發(fā)育和蛹形成時期有著重要作用。另外的6個Cecropins家族成員〔BmcecA3,BmcecA4和BmcecB3-BmcecB5以及BmcecC為在家蠶基因組精細(xì)圖繪制后,利用同源比對搜尋獲得的,活性檢測尚未有報(bào)道。但是新找到的BmcecB3-BmcecB5與BmcecB1,B2的氨基酸序列完全一致,核苷酸序列的差異也較小,只是在基因組中所處位置有所不同,推測可能具有同樣的抗菌活性。從基因組已經(jīng)測序完成的幾個模式生物來看,家蠶Cecropins家族成員數(shù)目顯著比黑腹果蠅〔5個和岡比亞按蚊〔4個多,這可能與家蠶缺乏專屬的類似于果蠅中Drosomycin的抗真菌肽有關(guān)。圖2家蠶Cecropin家族成員的多序列比對及二級結(jié)構(gòu)預(yù)測。紅色框表示螺旋區(qū)域,藍(lán)色框表示發(fā)夾結(jié)構(gòu)。結(jié)果由PSIPRED在線網(wǎng)站預(yù)測。Fig.2.SequencealignmentandsecondarystructurepredictionofCecropinsinBombyx.mori.Redboxesrepresenthelix;Blueboxrepresentscoil.TheresultswereobtainedbyusingtheonlineserverofthePSIPREDProteinStructurePrediction.1998年Kim等人用探針雜交的方法在家蠶中首先發(fā)現(xiàn)了Enbocin的片段ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[14],Kaneko等人又在20XX獲得了3個Enbocin基因的全長序列ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[15]。從氨基酸序列來看,Enbocin屬于Cecropins家族,可能是較早從Cecropin家族中分化出來,但是它們表現(xiàn)出相反的抗菌活性,Cecropins抗革蘭氏陰性菌的能力更強(qiáng),而Enbocin對革蘭氏陽性菌的抗性明顯強(qiáng)于對革蘭氏陰性菌的抗性。Cheng等人在家蠶基因組中只發(fā)現(xiàn)了2個編碼Enbocin基因—Bmenb1和Bmenb2,如圖1所示,這兩個基因與Cecropins基因成簇地排列在同一條染色體上,通過對Cheng等人發(fā)現(xiàn)的2個Enbocin與Kaneko的3個Enbocin氨基酸序列比較分析,Bmenb1和Bmenb2可以與Kaneko的Bmenb3和Bmenb2一一對應(yīng),而家蠶基因組中并未發(fā)現(xiàn)Kaneko所說的Bmenb,這可能是因?yàn)榧倚Q基因組測序并不完整所致。2.2Moricin家族Moricin是由HaraandYamakawa〔1995首先從家蠶血淋XX分離得到的ADDINEN.CITE<EndNote><Cite><Author>Hetru</Author><Year>2003</Year><RecNum>69</RecNum><record><rec-number>69</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hetru,C.</author><author>Troxler,L.</author><author>Hoffmann,J.A.</author></authors></contributors><auth-address>InstitutdeBiologieMoleculaireetCellulaire,UPR9022duCentreNationaldelaRechercheScientifique,Strasbourg,France.</auth-address><titles><title>Drosophilamelanogasterantimicrobialdefense</title><secondary-title>JInfectDis</secondary-title></titles><periodical><full-title>JInfectDis</full-title></periodical><pages>S327-34</pages><volume>187Suppl2</volume><keywords><keyword>Animals</keyword><keyword>BacterialInfections/immunology</keyword><keyword>Drosophilamelanogaster/genetics/*immunology</keyword><keyword>*Immunity,Natural</keyword><keyword>Mycoses/immunology</keyword><keyword>ParasiticDiseases,Animal/immunology</keyword><keyword>Peptides/immunology</keyword><keyword>SignalTransduction</keyword></keywords><dates><year>2003</year><pub-dates><date>Jun15</date></pub-dates></dates><accession-num>12792847</accession-num><urls><related-urls><url>/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=12792847</url></related-urls></urls></record></Cite></EndNote>[16],它對革蘭氏陰性菌和革蘭氏陽性菌均有強(qiáng)烈的抗菌活性。家蠶抗菌肽Moricin由65-66個氨基酸殘基組成,在其N-末端部分每隔3～4個氨基酸殘基就有帶電荷氨基酸,只形成1個長的具有親水脂性質(zhì)的α-螺旋結(jié)構(gòu)<圖3>,在C-末端則存在堿性氨基酸殘基串,而且沒有發(fā)現(xiàn)Moricin有氨基酸的修飾。其抗菌機(jī)理可能是利用堿性C端與細(xì)胞膜表面作用,然后利用N端改變膜的通透性,形成離子通道ADDINEN.CITE<EndNote><Cite><Author>Hemmi</Author><Year>2002</Year><RecNum>67</RecNum><record><rec-number>67</rec-number><ref-typename="JournalArticle">17</ref-type><contributors><authors><author>Hemmi,H.</author><author>Ishibashi,J.</author><author>Hara,S.</author><author>Yamakawa,M.</author></authors></contributors><auth-address>NationalFoodResearchInstitute,2-1-12Kannondai,Tsukuba,Ibaraki305-8642,Japan.hemmi@nfri.affrc.go.jp</auth-address><titles><title>Solutionstructureofmoricin,anantibacterialpeptide,isolatedfromthesilkwormBombyxmori</ti