Intragenic suppressors of P-loop mutations in the beta-subunit of the mitochondrial ATPase in the yeast Saccharomyces cerevisiae.
Three intragenic second-site suppressors, P353L, T237I, and L390F, were identified that suppressed two mutations in, and one adjacent to, the P-loop in the beta-subunit of the yeast F1-ATPase. The crystal structure of bovine F1-ATPase (Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628) shows that these suppressor residues are located in the nucleotide-binding domain. Specific hypotheses have been formulated that suggest the conformational coupling of the P-loop with the suppressor sites. P353L is in a "catch" region, which forms unique interactions with the gamma-subunit in the three different conformational states of the catalytic site. The identification of this suppressor mutation demonstrates genetically that the catch region is conformationally coupled to the P-loop. T237I is shown to interact with Lys-209, which occurs just after the P-loop. This suggests that this interaction changes the conformation of the P-loop to suppress the initial mutation. L390F interacts with Ala-181, which is adjacent to the P-loop. The mechanism of this suppression is suggested to occur through the interactions of L390F with Ala-181. These results identify critical interactions that modulate the structure of the P-loop and thus the biochemistry of the enzyme.
Shen
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Department of Biological Chemistry, Chicago Medical School, North Chicago, Illinois 60064, USA.
Sosa-Peinado
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A
Mueller
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DM
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013489:Suppression, Genetic
D000251:Adenosine Triphosphatases