IDENTIFICATION OF A CROSS-LINKED DOUBLE-PEPTIDE FROM THE CATALYTIC SITE OF THE CA2-ATPASE OF SARCOPLASMIC-RETICULUM FORMED BY THE CA2+-DEPENDENT AND PH-DEPENDENT REACTION WITH ATP GAMMA-P-IMIDAZOLIDATE()

The Ca2+-ATPase from sarcoplasmic reticulum can be inhibited by the Ca 2+- and pH-dependent reaction with ATPgammaP-imidazolidate. The chemic ally and monofunctionally activated inhibitor introduces an intramolec ular cross-link between two neighbouring peptides of the active site. This can be followed by the reduced mobility of the ATPase upon SDS-PA GE analysis which becomes even more pronounced after limited trypsinol ysis. After cleavage of the cross-linked ATPase molecule by cyanogen b romide and separation of the peptides a double-peptide can be detected which upon sequencing can be identified as part of the phosphorylatio n and the nucleotide binding site, respectively.