Allosteric inhibitors of plasma membrane Ca2+ pumps: Invention and applications of caloxins

Table 1 Structure activity relationship of caloxin 1c2 like peptides[64]

Caloxin	Peptide sequence	Ki (μmol/L)
1b1	TAWSEVLHLLSR GGGSK	45 ± 4
1c1	TTWSEVVHRLSR GGGSK	20 ± 3
1c3	ASWSEVLHLLSR GGGSK	18 ± 3
1c2	TAWSEVLDLLRR GGGSK	2.3 ± 0.3
3B1c2biotin	TABSEVLDLLRR GGGSK(biotin)-amide	50 ± 6
16B1c2biotin	TAWSEVLDLLRR GGGBK(biotin)-amide	5.1 ± 0.8

Caloxins 1c1, 1c2 and 1c3 were obtained by random limited mutagenesis of caloxin 1b1. The values of inhibition constants (Ki) are for plasma membrane Ca²⁺ pump (PMCA) ATPase in the human erythrocyte ghosts, which contain mostly PMCA4. B: Benzoylphenylalanine.