VLIP, a viral lipase homologue, is a virulence factor of Marek's disease virus
VLIP, a viral lipase homologue, is a virulence factor of Marek's disease virus
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DOI：
10.1128/jvi.79.11.6984-6996.2005
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发表时间：
2005-06-01
影响因子：
5.4
通讯作者：
Kung, HJ
中科院分区：
文献类型：
--
作者：
Kamil, JP;Tischer, BK;Kung, HJ
马立克氏病病毒（Marek's disease virus， MDV）的基因组已被预测编码一种分泌糖蛋白vLIP，该糖蛋白与胰腺脂肪酶的α / β水解酶折叠具有显著的同源性。这里证明了MDV vLIP mRNA是通过剪接产生的，并且由于其对DNA复制抑制的敏感性，vLIP是一个晚期基因。虽然vLIP被发现保留了水解酶活性所必需的几个残基，但在脂肪酶催化三酸位点存在不利的天冬酰胺取代。与结构预测一致，纯化的重组vLIP在传统磷脂或甘油三酯底物上没有可检测到的活性。两种不同的vLIP突变病毒，一种在脂肪酶同源结构域有173个氨基酸缺失，另一种在丝氨酸亲核位点有丙氨酸点突变，导致鸡马立克病的发病率显著降低，相对于两种独立产生的vLIP逆转录病毒或亲本病毒，存活率提高。这些数据提供了vLIP增强MDV复制和致病潜力的第一个证据。此外，虽然vLIP可能不是传统的脂肪酶，但数据表明，丝氨酸亲核位点对于vLIP的病毒功能在体内仍然是必不可少的。因此，这个脂肪酶同源性的特殊例子可能代表了α / β水解酶折叠向非酶作用的重新利用，可能在脂质键合中。
The genome of Marek's disease virus (MDV) has been predicted to encode a secreted glycoprotein, vLIP, which bears significant homology to the alpha/beta hydrolase fold of pancreatic lipases. Here it is demonstrated that MDV vLIP mRNA is produced via splicing and that vLIP is a late gene, due to its sensitivity to inhibition of DNA replication. While vLIP was found to conserve several residues essential to hydrolase activity, an unfavorable asparagine substitution is present at the lipase catalytic triad acid position. Consistent with structural predictions, purified recombinant vLIP did not show detectable activity on traditional phospholipid or triacylglyceride substrates. Two different vLIP mutant viruses, one bearing a 173-amino-acid deletion in the lipase homologous domain, the other having an alanine point mutant at the serine nucleophile position, caused a significantly lower incidence of Marek's disease in chickens and resulted in enhanced survival relative to two independently produced vLIP revertants or parental virus. These data provide the first evidence that vLIP enhances the replication and pathogenic potential of MDV. Furthermore, while vLIP may not serve as a traditional lipase enzyme, the data indicate that the serine nucleophile position is nonetheless essential in vivo for the viral functions of vLIP. Therefore, it is suggested that this particular example of lipase homology may represent the repurposing of an alpha/beta hydrolase fold toward a nonenzymatic role, possibly in lipid bonding.