Document Detail

Histidine-49 is necessary for the pH-dependent transition between active and inactive states of the bovine F1-ATPase inhibitor protein.
MedLine Citation:
PMID:  8597569     Owner:  NLM     Status:  MEDLINE    
The role of the histidyl residue at position 49 (H49) of the bovine mitochondrial F1-ATPase inhibitor protein (F1I) was examined by site-directed mutagenesis. Six amino acids (Q, E, K, V, L, and I) were substituted for H49 and the activities of the resulting inhibitor proteins were characterized with respect to pH. Each of the six mutations abolished the pH sensitivity which is characteristic of wild-type F1I. At pH 8.0 each of the mutations caused an increase in apparent maximum inhibition and a decrease in apparent Ki relative to wild type. At pH 6.7 the hydrophilic substitutions had little effect on apparent Ki, while the hydrophobic substitutions caused increases of 3.5- to 8.5-fold relative to wild type. The ratios of apparent Ki at pH 8.0 to apparent Ki at pH 6.7 were in the range of 0.5 to 1.6 for the mutants, whereas the wild-type value is 15.0. The mutations appear to shift the equilibrium between active and inactive conformations of F1I toward the active state. We find that H49 is required by F1I for sensitivity to pH and that it may facilitate the transition between active and inactive states of F1I. A possible role for H49 in the stabilization of the inactive state through participation in a multivalent complex with Zn2+ is also discussed.
R Schnizer; G Van Heeke; D Amaturo; S M Schuster
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1292     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1996 Feb 
Date Detail:
Created Date:  1996-04-22     Completed Date:  1996-04-22     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  241-8     Citation Subset:  IM    
Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.
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MeSH Terms
Amino Acid Sequence
Binding Sites
Chlorides / pharmacology
Hydrogen-Ion Concentration
Mitochondria, Heart / metabolism
Molecular Sequence Data
Mutagenesis, Site-Directed
Point Mutation
Protein Biosynthesis
Proteins / chemistry*,  pharmacology*
Proton-Translocating ATPases / antagonists & inhibitors*
Recombinant Proteins / biosynthesis,  chemistry,  pharmacology
Zinc Compounds / pharmacology
Reg. No./Substance:
0/ATPase inhibitory protein; 0/Chlorides; 0/Codon; 0/Proteins; 0/Recombinant Proteins; 0/Zinc Compounds; 71-00-1/Histidine; 7646-85-7/zinc chloride; EC ATPases

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