Kalpaini su sveprisutna, dobro konzervirana porodica cisteinskih proteaza ovisnih o kalciju. Porodice kalpaina su uključene u neurodegenerativne procese, jer njihova aktivacija može biti izazvana prilivom kalcija i oksidativnim stresom. Kalpain I i II su heterodimeri sa različitim velikim podjedinicama povezanim sa zajedničkim malim podjedinicama, koje su sve kodirane različitim genima. Mala regulatorna podjedinica sastoji se od N-terminalnog domena, koji sadrži oko 30% ostataka glicina i C-terminalnog Ca-vezujućeg domena.[4] Two transcript variants encoding the same protein have been identified for this gene.[3]
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Ohno S, Minoshima S, Kudoh J, Fukuyama R, Shimizu Y, Ohmi-Imajoh S, Shimizu N, Suzuki K (1990). "Four genes for the calpain family locate on four distinct human chromosomes". Cytogenetics and Cell Genetics. 53 (4): 225–9. doi:10.1159/000132937. PMID2209092.
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