THE STRUCTURE OF BACTERIOPHAGE-T7 LYSOZYME, A ZINC AMIDASE AND AN INHIBITOR OF T7 RNA-POLYMERASE
THE STRUCTURE OF BACTERIOPHAGE-T7 LYSOZYME, A ZINC AMIDASE AND AN INHIBITOR OF T7 RNA-POLYMERASE
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DOI：
10.1073/pnas.91.9.4034
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发表时间：
1994-04-26
影响因子：
11.1
通讯作者：
STUDIER, FW
中科院分区：
文献类型：
--
作者：
CHENG, XD;ZHANG, X;STUDIER, FW
噬菌体 T7 的溶菌酶是一种双功能蛋白，可切割细菌细胞壁中的酰胺键，并与 T7 RNA 聚合酶结合并抑制转录。突变型 T7 溶菌酶的结构已通过 X 射线晶体学确定，并以 2.2 埃分辨率进行了精修。该蛋白质折叠成具有明显裂口的α/β片层结构。一个锌原子位于裂缝中，直接与三个氨基酸结合，并通过水分子与第四个氨基酸结合。酰胺酶活性需要锌，但 T7 RNA 聚合酶的抑制不需要锌。 T7 溶菌酶的锌配体与羧肽酶 A 和嗜热菌蛋白酶的锌配体的比对表明酰胺酶和这些锌蛋白酶的催化位点之间的结构相似性。突变分析确定了裂缝内酰胺酶活性的假定催化残基以及似乎是与 T7 RNA 聚合酶结合的位点的表面。 T7 RNA 聚合酶的结合抑制酰胺酶活性。
The lysozyme of bacteriophage T7 is a bifunctional protein that cuts amide bonds in the bacterial cell wall and binds to and inhibits transcription by T7 RNA polymerase. The structure of a mutant T7 lysozyme has been determined by x-ray crystallography and refined at 2.2-Angstrom resolution. The protein folds into an alpha/beta-sheet structure that has a prominent cleft. A zinc atom is located in the cleft, bound directly to three amino acids and, through a water molecule, to a fourth. Zinc is required for amidase activity but not for inhibition of T7 RNA polymerase. Alignment of the zinc ligands of T7 lysozyme with those of carboxypeptidase A and thermolysin suggests structural similarity among the catalytic sites for the amidase and these zinc proteases. Mutational analysis identified presumed catalytic residues for amidase activity within the cleft and a surface that appears to be the site of binding to T7 RNA polymerase. Binding of T7 RNA polymerase inhibits amidase activity.