Mycobacteriophage Lysin B is a novel mycolylarabinogalactan esterase
Mycobacteriophage Lysin B is a novel mycolylarabinogalactan esterase
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DOI：
10.1111/j.1365-2958.2009.06775.x
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发表时间：
2009-08-01
影响因子：
3.6
通讯作者：
Hatfull, Graham F.
中科院分区：
文献类型：
--
作者：
Payne, Kimberly;Sun, Qingan;Hatfull, Graham F.
分枝杆菌噬菌体在革兰氏阳性菌群中遇到一个独特的问题，即裂解不仅必须降解肽聚糖层，而且还必须绕过共价连接到阿拉伯半乳聚糖-肽聚糖复合物的富含分枝菌酸的外膜。分枝杆菌噬菌体通过产生两种裂解酶来实现这一点，即水解肽聚糖的赖氨酸A（LysA）和裂解分枝菌酰半乳聚糖键以释放游离分枝菌酸的新型分枝菌酰半乳聚糖酯酶赖氨酸B（LysB）。D29 LysB结构显示具有角质酶常见的催化三联体的α/β水解酶组织，但其含有涉及脂质底物结合的额外四螺旋结构域。尽管LysA是分枝杆菌裂解所必需的，但Giles DlysB突变体分枝杆菌噬菌体是有活力的，但在宿主细胞裂解的正常时机、进展和完成方面有缺陷。我们认为LysB通过损害分枝杆菌外膜与阿拉伯半乳聚糖-肽聚糖层连接的完整性来促进裂解。
Mycobacteriophages encounter a unique problem among phages of Gram-positive bacteria, in that lysis must not only degrade the peptidoglycan layer but also circumvent a mycolic acid-rich outer membrane covalently attached to the arabinogalactan-peptidoglycan complex. Mycobacteriophages accomplish this by producing two lysis enzymes, Lysin A (LysA) that hydrolyses peptidoglycan, and Lysin B (LysB), a novel mycolylarabinogalactan esterase, that cleaves the mycolylarabinogalactan bond to release free mycolic acids. The D29 LysB structure shows an alpha/beta hydrolase organization with a catalytic triad common to cutinases, but which contains an additional four-helix domain implicated in the binding of lipid substrates. Whereas LysA is essential for mycobacterial lysis, a Giles DlysB mutant mycobacteriophage is viable, but defective in the normal timing, progression and completion of host cell lysis. We propose that LysB facilitates lysis by compromising the integrity of the mycobacterial outer membrane linkage to the arabinogalactan-peptidoglycan layer.