TY - JOUR
T1 - The properties of hybrid F1-ATPase enzymes suggest that a cyclical catalytic mechanism involving three catalytic sites occurs
AU - Rao, R.
AU - Senior, A. E.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1987
Y1 - 1987
N2 - Maximal rates of ATP hydrolysis catalyzed by F1-ATPase enzymes are known to involve strong positive catalytic site cooperativity. There are three potential catalytic nucleotide-binding sites on F1. Two important and unanswered questions are (i) whether all three potential catalytic sites must interact cooperatively to yield maximal rates of ATP hydrolysis and (ii) whether a cyclical three-site mechanism operates as suggested by several authors. We have studied these two questions here by measuring the ATPase activities of hybrid enzymes containing normal β-, γ-, δ-, and ε-subunits together with different combinations of mutant and normal α-subunits. The mutant α-subunits were derived from uncA401, uncA447, and uncA453 mutant E. coli F1-ATPase, in which positive cooperativity between catalytic sites is strongly attenuated by defined mis-sense mutations. Our data show that three normal catalytic sites are required to interact in order to achieve maximal ATPase rates and suggest that a cyclical mechanism does operate. Hybrid enzyme containing one-third mutant α-subunit and two-thirds normal α-subunits had substantial but submaximal activity, showing that cooperativity between three sites in a noncyclical fashion, or between pairs of sites, can achieve effective catalysis.
AB - Maximal rates of ATP hydrolysis catalyzed by F1-ATPase enzymes are known to involve strong positive catalytic site cooperativity. There are three potential catalytic nucleotide-binding sites on F1. Two important and unanswered questions are (i) whether all three potential catalytic sites must interact cooperatively to yield maximal rates of ATP hydrolysis and (ii) whether a cyclical three-site mechanism operates as suggested by several authors. We have studied these two questions here by measuring the ATPase activities of hybrid enzymes containing normal β-, γ-, δ-, and ε-subunits together with different combinations of mutant and normal α-subunits. The mutant α-subunits were derived from uncA401, uncA447, and uncA453 mutant E. coli F1-ATPase, in which positive cooperativity between catalytic sites is strongly attenuated by defined mis-sense mutations. Our data show that three normal catalytic sites are required to interact in order to achieve maximal ATPase rates and suggest that a cyclical mechanism does operate. Hybrid enzyme containing one-third mutant α-subunit and two-thirds normal α-subunits had substantial but submaximal activity, showing that cooperativity between three sites in a noncyclical fashion, or between pairs of sites, can achieve effective catalysis.
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M3 - Article
C2 - 2891693
AN - SCOPUS:0023522190
SN - 0021-9258
VL - 262
SP - 17450
EP - 17454
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 36
ER -