Calpain small subunit 1, also known as CAPN4, is a protein that in humans is encoded by the CAPNS1gene.
Calpains are a ubiquitous, well-conserved family of calcium-dependent, cysteine proteases. Calpain families have been implicated in neurodegenerative processes, as their activation can be triggered by calcium influx and oxidative stress. Calpain I and II are heterodimeric with distinct large subunits associated with common small subunits, all of which are encoded by different genes. The small regulatory subunit consists of an N-terminal domain, containing about 30% glycine residues and a C-terminal Ca-binding domain. Two transcript variants encoding the same protein have been identified for this gene.
^Lin GD, Chattopadhyay M, Maki KKW, Wang M, Carson L, Jin PW, Yuen E, Takano M, Hatanaka LJ, Narayana SVL. Crystal structure of calcium bound domain VI of calpain at 1.9A resolution and its role in enzyme assembly, regulation, and inhibitor binding. Nat Struct Biol 1997; 4(7):539–547.
Reverter D, Sorimachi H, Bode W (2001). "The structure of calcium-free human m-calpain: implications for calcium activation and function". Trends Cardiovasc. Med. 11 (6): 222–9. doi:10.1016/S1050-1738(01)00112-8. PMID11673052.
Banik NL, DeVries GH, Neuberger T, et al. (1991). "Calcium-activated neutral proteinase (CANP; calpain) activity in Schwann cells: immunofluorescence localization and compartmentation of mu- and mCANP". J. Neurosci. Res. 29 (3): 346–54. doi:10.1002/jnr.490290310. PMID1656060.
Ohno S, Minoshima S, Kudoh J, et al. (1990). "Four genes for the calpain family locate on four distinct human chromosomes". Cytogenet. Cell Genet. 53 (4): 225–9. doi:10.1159/000132937. PMID2209092.
Andersson B, Wentland MA, Ricafrente JY, et al. (1996). "A "double adaptor" method for improved shotgun library construction". Anal. Biochem. 236 (1): 107–13. doi:10.1006/abio.1996.0138. PMID8619474.
Zhang W, Lane RD, Mellgren RL (1996). "The major calpain isozymes are long-lived proteins. Design of an antisense strategy for calpain depletion in cultured cells". J. Biol. Chem. 271 (31): 18825–30. doi:10.1074/jbc.271.31.18825. PMID8702541.