Kumar Atul, Kumar Sanjiv, Kumar Dilip, Mishra Arpit, Dewangan Rikeshwer P, Shrivastava Priyanka, Ramachandran Srinivasan, Taneja Bhupesh
Structural Biology Unit, CSIR-IGIB, South Campus, Mathura Road, New Delhi 110 025, India.
Acta Crystallogr D Biol Crystallogr. 2013 Dec;69(Pt 12):2543-54. doi: 10.1107/S0907444913026371. Epub 2013 Nov 19.
Bacterial N-acetylmuramoyl-L-alanine amidases are cell-wall hydrolases that hydrolyze the bond between N-acetylmuramic acid and L-alanine in cell-wall glycopeptides. Rv3717 of Mycobacterium tuberculosis has been identified as a unique autolysin that lacks a cell-wall-binding domain (CBD) and its structure has been determined to 1.7 Å resolution by the Pt-SAD phasing method. Rv3717 possesses an α/β-fold and is a zinc-dependent hydrolase. The structure reveals a short flexible hairpin turn that partially occludes the active site and may be involved in autoregulation. This type of autoregulation of activity of PG hydrolases has been observed in Bartonella henselae amidase (AmiB) and may be a general mechanism used by some of the redundant amidases to regulate cell-wall hydrolase activity in bacteria. Rv3717 utilizes its net positive charge for substrate binding and exhibits activity towards a broad spectrum of substrate cell walls. The enzymatic activity of Rv3717 was confirmed by isolation and identification of its enzymatic products by LC/MS. These studies indicate that Rv3717, an N-acetylmuramoyl-L-alanine amidase from M. tuberculosis, represents a new family of lytic amidases that do not have a separate CBD and are regulated conformationally.
细菌N-乙酰胞壁酰-L-丙氨酸酰胺酶是一种细胞壁水解酶，可水解细胞壁糖肽中N-乙酰胞壁酸和L-丙氨酸之间的键。结核分枝杆菌的Rv3717已被鉴定为一种独特的自溶素，它缺乏细胞壁结合结构域（CBD），并且通过Pt-SAD相位法确定其结构的分辨率为1.7 Å。Rv3717具有α/β折叠，是一种锌依赖性水解酶。该结构揭示了一个短的柔性发夹环，它部分封闭了活性位点，可能参与了自我调节。在汉氏巴尔通体酰胺酶（AmiB）中观察到了这种肽聚糖水解酶活性的自我调节类型，它可能是一些冗余酰胺酶用于调节细菌细胞壁水解酶活性的一种普遍机制。Rv3717利用其净正电荷进行底物结合，并对多种底物细胞壁表现出活性。通过LC/MS分离和鉴定其酶促产物，证实了Rv3717的酶活性。这些研究表明，来自结核分枝杆菌的N-乙酰胞壁酰-L-丙氨酸酰胺酶Rv3717代表了一类新的裂解酰胺酶家族，它们没有单独的CBD，而是通过构象进行调节。
