title: Properties and intracellular localization of calpain activator protein.
abstract: In this paper, we have further analyzed the properties of calpain activator (CA) in order to better define its physiological function. The activator shows a pH optimum approximately 7.8-8.0, independently of the nature of the buffer used. Although the maximal activity is observed with human acid-denatured globin, the effect of CA is detectable with other protein substrates, such as casein and insulin. A comparable activating effect is observed also with the synthetic substrate Succ-Leu-Tyr-AMC. The activatory effect has been evaluated in a reconstructed system, using plasma membrane Ca(2+)-ATPase as substrate. CA is localized in erythrocyte precursor cells on the inner surface of the plasma membrane in very high amount and its level profoundly decreases up to 10% of the original value when cells reach the terminal differentiated state.
authors.affiliation: Department of Experimental Medicine-Biochemistry Section, University of Genoa, Italy. melloni@csita.it
authors.forename: E
authors.initials: E
authors.lastname: Melloni
authors.forename: R
authors.initials: R
authors.lastname: Minafra
authors.forename: F
authors.initials: F
authors.lastname: Salamino
authors.forename: S
authors.initials: S
authors.lastname: Pontremoli
mesh_terms: D000818:Animals; D002021:Buffers; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism; D002454:Cell Differentiation; D004789:Enzyme Activation / Q000187:drug effects; D020536:Enzyme Activators / Q000378:metabolism* / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000378:metabolism; D005914:Globins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D011489:Protein Denaturation; D011506:Proteins / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D013379:Substrate Specificity / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D002021:Buffers; D002364:Caseins; D020536:Enzyme Activators; D007328:Insulin; D008565:Membrane Proteins; D011506:Proteins; C410340:calpain activator; D005914:Globins; D002154:Calpain; D000252:Calcium-Transporting ATPases