Chiu C H, Lee C Z, Lin K S, Tam M F, Lin L Y
Institute of Radiation Biology and Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.
J Bacteriol. 1999 Aug;181(15):4686-9. doi: 10.1128/JB.181.15.4686-4689.1999.
Amino acid residues in the metal-binding and putative substrate-binding sites of Escherichia coli methionine aminopeptidase (MAP) were mutated, and their effects on the function of the enzyme were investigated. Substitution of any amino acid residue at the metal-binding site resulted in complete loss of the two cobalt ions bound to the protein and diminished the enzyme activity. However, only Cys70 and Trp221 at the putative substrate-binding site are involved in the catalytic activity of MAP. Changing either of them caused partial loss of enzyme activity, while mutations at both positions abolished MAP function. Both residues are found to be conserved in type I but not type II MAPs.
对大肠杆菌甲硫氨酸氨肽酶（MAP）的金属结合位点和假定的底物结合位点中的氨基酸残基进行了突变，并研究了它们对酶功能的影响。金属结合位点上任何氨基酸残基的取代都会导致与蛋白质结合的两个钴离子完全丧失，并降低酶活性。然而，在假定的底物结合位点上只有Cys70和Trp221参与MAP的催化活性。改变其中任何一个都会导致酶活性部分丧失，而两个位置的突变则会消除MAP的功能。发现这两个残基在I型MAP中保守，但在II型MAP中不保守。
