Cardiac high molecular weight calmodulin-binding protein is homologous to calpastatin I and calpastatin II.
Calpastatin is an endogenous inhibitor of calpain, which has been implicated in various physiological and pathological processes. In the present study we determined the molecular and inhibitory properties of HMWCaMBP, calpastatin I, and calpastatin II. Western blot analysis with antibodies raised against either full length HMWCaMBP or internal peptides that are common to all isoforms showed that all three homologs have common antigenic epitopes. However, additional Western blot analysis with N-terminal specific antibodies showed that all three proteins are different at the N-terminal end. HMWCaMBP is clearly different from two other homologues, calpastatin I and II, at the N-terminal end. In addition, HMWCaMBP also showed the same affinities for m-calpain as calpastatin I and calpastatin II. Our findings suggest that HMWCaMBP is the homolog of calpastatin and may be a CaM-binding form of calpastatin.
Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan, Canada S7N 0W8.
Nisha
N
Singh
Anuraag
A
Shrivastav
Doug
D
Olson
Ashakumary
A
Lakshmikuttyamma
Andrew
A
Ross
Tim
T
Parr
Ronald G
RG
Bardsley
Rajendra K
RK
Sharma
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D002417:Cattle; D006321:Heart; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010449:Peptide Mapping; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; C033668:calpastatin; D002154:Calpain