PMID:9425083
| Citation |
Weber, J, Hammond, ST, Wilke-Mounts, S and Senior, AE (1998) Mg2+ coordination in catalytic sites of F1-ATPase. Biochemistry 37:608-14 |
|---|---|
| Abstract |
Coordination of the Mg2+ ion in Mg-nucleotide substrates by amino acid residue side chains in the catalytic site of Escherichia coli F1-ATPase was investigated. From the X-ray structure of the mitochondrial enzyme [Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628], it may be inferred that the hydroxyl of betaThr-156 is a direct ligand of Mg2+, whereas the carboxyls of betaGlu-181, betaGlu-185, and betaAsp-242 might contribute via intervening water molecules. Elimination of each respective functional group by site-directed mutagenesis, followed by determination of Mg-nucleotide and uncomplexed nucleotide binding affinities using a tryptophan probe, showed that betaThr-156, betaGlu-185, and betaAsp-242 are all involved in Mg2+ coordination, whereas betaGlu-181 is not. A derived structural model for the octahedral coordination around the Mg2+ ion is presented. The results indicate that the ADP-containing site in the X-ray structure is the catalytic site of highest affinity. Correct Mg2+ coordination is required for catalytic activity at physiological rates. Elimination of any one of the Mg2+-coordinating residues led to complete loss of Mg2+-dependent nucleotide binding cooperativity of the catalytic sites. |
| Links |
PubMed Online version:10.1021/bi972370e |
| Keywords |
Adenine Nucleotides/metabolism; Adenosine Diphosphate/metabolism; Adenosine Triphosphate/metabolism; Binding Sites; Escherichia coli/enzymology; Magnesium/metabolism; Models, Chemical; Mutagenesis, Site-Directed; Proton-Translocating ATPases/genetics; Proton-Translocating ATPases/metabolism |
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