CAJ | 학술논문

营养期杀虫蛋白(Vip)是苏云金杆菌在营养期所产生的一类新型杀虫蛋白,代表了第二代转基因杀虫蛋白,它能在一定程度上克服许多害虫对δ-内毒素低敏感或者不敏感的缺陷.但是,目前和已经深入研究的δ-内毒素相比较,有关Vip蛋白结构和功能关系方面的报道还甚少.本文采用最大似然方法和基于最大简约的滑窗分析对Vip蛋白的分子进化机制进行了评价.结果发现Vip蛋白在进化过程当中经历了正选择,并采用贝叶斯方法确定了16个正选择氨基酸残基.有意思的是所有这些正选择残基都位于Vip蛋白C端从705到809的区域.当把这些正选择残基定位到二级结构和三级结构时,发现绝大部分正选择残基都暴露在Vip蛋白空间结构的表面并且聚集在环的区域.推测Vip蛋白分子进化的机制应该是受到了正选择压力而不是功能约束的松弛.导致Vip蛋白C端多样性的潜在正选择压力可能是Vip蛋白为了在和目标昆虫之间竞争取得优势,或者是为了扩大Vip蛋白的杀虫范围.文中确定的经历了正选择残基很有可能是和昆虫宿主范围有关,因此可以为今后研究Vip蛋白的结构和功能提供相应的靶点.
영양기살충단백(Vip)시소운금간균재영양기소산생적일류신형살충단백,대표료제이대전기인살충단백,타능재일정정도상극복허다해충대δ-내독소저민감혹자불민감적결함.단시,목전화이경심입연구적δ-내독소상비교,유관Vip단백결구화공능관계방면적보도환심소.본문채용최대사연방법화기우최대간약적활창분석대Vip단백적분자진화궤제진행료평개.결과발현Vip단백재진화과정당중경력료정선택,병채용패협사방법학정료16개정선택안기산잔기.유의사적시소유저사정선택잔기도위우Vip단백C단종705도809적구역.당파저사정선택잔기정위도이급결구화삼급결구시,발현절대부분정선택잔기도폭로재Vip단백공간결구적표면병차취집재배적구역.추측Vip단백분자진화적궤제응해시수도료정선택압력이불시공능약속적송이.도치Vip단백C단다양성적잠재정선택압력가능시Vip단백위료재화목표곤충지간경쟁취득우세,혹자시위료확대Vip단백적살충범위.문중학정적경력료정선택잔기흔유가능시화곤충숙주범위유관,인차가이위금후연구Vip단백적결구화공능제공상응적파점.
Vegetative insecticidal proteins(VIPs),produced during the vegetative stage of their growth in Bacillus thuringiensis,are a group of insecticidal proteins and represent the second generation of insecticidal trans-genes that will complement the novel δ-endotoxins in future.Fewer structural and functional relationships of Vip proteins are known in comparison with those of δ-endotoxins.In this study,both the maximum-likelihood methods and the maximum parsimony based sliding window analysis were used to evaluate the molecular evolution of Vip proteins.As a result,strong evidence was found that Vip proteins are subject to the high rates of positive selection,and 16 sites are identified to be under positive selection using the Bayes Empirical Bayesian method.Interestingly,all these positively selected sites are located from site-705 to site-809 in the C-terminus of the Vip proteins.Most of these sites are exposed and clustered in the loop regions when mapped onto its computational predicted secondary tertiary and a part of the tertiary structure.It has been postulated that the high divergence in the C-terminal of Vip proteins may not result from the lack of functional constraints,but rather from the rapid mutation to adapt their targeted insects,driven by positive selection.The potential positive selection pressures may be an attempt to adapt for the"arm race"between Vip proteins and the targeted insects,or to enlarge their target's host range.Sites identified to be under positive selection may be related to the insect host range,which may shed a light on the investigation of the Vip proteins'structural and functional relationships.