Exon-intron structure of outlier tick lipocalins indicate a monophyletic origin within the larger lipocalin family
Exon-intron structure of outlier tick lipocalins indicate a monophyletic origin within the larger lipocalin family
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DOI：
10.1016/j.ibmb.2004.03.006
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发表时间：
2004-06-01
影响因子：
3.8
通讯作者：
Neitz, AWH
中科院分区：
文献类型：
--
作者：
Mans, BJ;Neitz, AWH
所有分配给脂质运载蛋白家族的蜱蛋白都缺乏内核脂质运载蛋白特有的结构保守区（SCR），因此可以归类为离群值。这些蜱蛋白已被分配到蜱脂质运载蛋白家族的基础上，数据库搜索表明蜱序列之间的同源性和事实，即组胺结合蛋白（HBP 2）从硬蜱扇头蜱（硬蜱科）显示结构相似性的脂质运载蛋白折叠。内核和异常脂质运载蛋白之间的序列同一性福尔斯低于20%，并且提出的问题是异常脂质运载蛋白和内核脂质运载蛋白是否真正同源。更具体地，在蜱脂质运载蛋白的情况下，无论它们的结构折叠是源自脂质运载蛋白折叠还是会聚进化导致产生基本的脂质运载蛋白样折叠，其由八链连续反平行β-桶组成，该桶由平行于桶的C-末端α-螺旋终止。目前的研究确定了HBP 2和TSGP 1，TSGP 2和TSGP 4的基因结构，从软蜱Ornithodoros savignyi（Argasidae）中鉴定出脂质运载蛋白。所有蜱脂质运载蛋白具有四个内含子（A-D），其在蜱脂质运载蛋白序列比对内具有保守的位置和相位。位置和相位信息相对于脂质运载蛋白家族的其余部分也是保守的。系统发育分析，使用这些信息表明，确凿的蜱脂质运载蛋白是进化相关的脂质运载蛋白家族的其余部分。蜱脂质运载蛋白被分组在一个单系进化枝内，这表明蜱谱系内的单系起源，并且还与其他节肢动物脂质运载蛋白分组在一个更大的进化枝中。基于脂质运载蛋白折叠的保守二级结构的序列比对的系统发育分析支持基因结构树的结论。这些结果表明，外显子-内含子排列可用于在较大的脂质运载蛋白家族内包含离群脂质运载蛋白。(C)2004爱思唯尔有限公司保留所有权利。
All tick proteins assigned to the lipocalin family lack the structural conserved regions (SCRs) that are characteristic of the kernel lipocalins and can thus be classified as outliers. These tick proteins have been assigned to the tick lipocalin family based on database searches that indicated homology between tick sequences and the fact that the histamine binding protein (HBP2) from the hard tick Rhipicephalus appendiculatus (Ixodidae) shows structural similarity to the lipocalin fold. Sequence identity between kernel and outlier lipocalins falls below 20% and the question raised is whether the outlier and kernel lipocalins are truly homologous. More specifically in the case of the tick lipocalins, whether their structural fold is derived from the lipocalin fold or whether convergent evolution resulted in the generation of the basic lipocalin-like fold which consists of an eight stranded continuous anti-parallel beta-barrel terminated by a C-terminal alpha-helix that lies parallel to the barrel. The current study determined the gene structure for HBP2 and TSGP1, TSGP2 and TSGP4, lipocalins identified from the soft tick Ornithodoros savignyi (Argasidae). All tick lipocalins have four introns (A-D) with conserved positions and phases within the tick lipocalin sequence alignment. The positions and phase information are also conserved with regard to the rest of the lipocalin family. Phylogenetic analysis using this information shows conclusively that tick lipocalins are evolutionary related to the rest of the lipocalin family. Tick lipocalins are grouped within a monophyletic clade that indicates a monophyletic origin within the tick lineage and also group with the other arthropod lipocalins in a larger clade. Phylogenetic analysis of sequence alignments based on conserved secondary structure of the lipocalin fold support the conclusions from the gene structure trees. These results indicate that exon-intron arrangement can be useful for the inclusion of outlier lipocalins within the larger lipocalin family. (C) 2004 Elsevier Ltd. All rights reserved.