A MUTATION AT GLY314 OF THE BETA SUBUNIT OF THE ESCHERICHIA-COLI PYRIDINE-NUCLEOTIDE TRANSHYDROGENASE ABOLISHES ACTIVITY AND AFFECTS THE NADP(H)-INDUCED CONFORMATIONAL CHANGE

被引:56
作者
AHMAD, S [1 ]
GLAVAS, NA [1 ]
BRAGG, PD [1 ]
机构
[1] UNIV BRITISH COLUMBIA,DEPT BIOCHEM,2146 HLTH SCI MALL,VANCOUVER V6T 1Z3,BC,CANADA
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1992年 / 207卷 / 02期
关键词
D O I
10.1111/j.1432-1033.1992.tb17103.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Escherichia coli RH1 contains a mutation causing complete loss of pyridine nucleotide transhydrogenase activity. A single base change in the chromosomal DNA resulted in the replacement of Gly314 of the beta-subunit by a Glu residue. The mutant enzyme was partially purified and its trypsin cleavage products examined. The distinct pattern of polypeptides given by proteolysis of the normal transhydrogenase in the presence of NADP(H) was absent when the mutant enzyme was treated with trypsin. However, the beta-subunit of the mutant enzyme retained its ability to bind to NAD-agarose. Further substitutions were made at Gly314 converting it to Ala, Val or Cys by the use of site-directed mutagenesis. All substitutions for Gly314 abolished the activity completely. The enzyme containing the Gly314 --> Ala mutation was studied in detail and behaved exactly as the enzyme containing the Gly314 -->Glu mutation. It is concluded that the mutation in the beta-subunit abolished the NADP(H)-induced conformational change in the mutant enzyme. This conformational change, caused by NADP(H) binding, is required to cleave the normal beta-subunit at Arg265 by trypsin. The genes encoding the pyridine nucleotide transhydrogenase were completely resequenced and several corrections have been made to the previously published sequence [Clarke et al. (1986) Eur. J. Biochem. 158, 647 - 653].
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页码:733 / 739
页数:7
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