JBC, Vol. 253, Issue 17, 6100-6106, Sep, 1978
Identification of a tyrosine residue at a nucleotide binding site in the beta subunit of the mitochondrial ATPase with p-fluorosulfonyl[14C]-benzoyl-5'-adenosine
F. S. Esch and W. S. Allison
The mitochondrial F1-ATPase is irreversibly inactivated by the adenine
nucleotide analogue, p-fluorosulfonylbenzoyl-5'-adenosine. This
inactivation is partly prevented by the presence of bound adenine
nucleotides. Inactivations of the ATPase with
p-fluorosulfonyl[14C]benzoyl-5'-adenosine were most efficiently
accomplished with the nucleotide-free enzyme at pH 7.0, in a buffer
containing 20% glycerol. Under these conditions, 4.2 g atoms of 14C are
incorporated per 350,000 g of enzyme when the ATPase is inactivated by 90%
by its reaction with 2 mM p-fluorosulfonyl[14C]benzoyl-5'-adenosine.
Isolation of the component polypeptide chains of the labeled ATPase showed
that all of the radioactivity was associated with the two largest subunits.
The isolated alpha subunit contained 0.45 g atom of 14C/mol and the
isolated beta subunit contained 0.88 g atom of 14C/mol. Hence, the
inactivation can be correlated with the incorporation of 14C into the beta
subunit. This suggests that the hydrolytic site of the enzyme resides on
this subunit. The majority of the radioactivity in a tryptic digest of
labeled beta subunit is contained ina tryptic peptide that has the
following amino acid sequence:
Ile-Met-Asp-Pro-Asn-Ile-Val-Gly-Ser-Glu-His-Tyr-Asp-Val-Ala-Arg, where Tyr
is the radioactive derivative of the tyrosine residue that was sulfonylated
during the inactivation.