Identification of a cross‐linked double‐peptide from the catalytic site of the Ca2+‐ATPase of sarcoplasmic reticulum formed by the Ca2+‐ and pH‐dependent reaction with ATP γP‐imidazolidate

Abstract
The Ca2+-ATPase from sarcoplasmic reticulum can be inhibited by the Ca2+- and pH-dependent reaction with ATP γP-imidazolidate. The chemically and monofunctionally activated inhibitor introduces an intramolecular cross-link between two neighbouring peptides of the active site. This can be followed by the reduced mobility of the ATPase upon SDS-PAGE analysis which becomes even more pronounced after limited trypsinolysis. After cleavage of the cross-linked ATPase molecule by cyanogen bromide and separation of the peptides a double-peptide can be detected which upon sequencing can be identified as part of the phosphorylation and the nucleotide binding site, respectively.

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