title: Similarity and dissimilarity in subunit structures of calpains I and II from various sources as demonstrated by immunological cross-reactivity.
abstract: The structural relationship between calpain I (low Ca2+-requiring) and calpain II (high Ca2+-requiring) molecules and their respective larger (80K) and smaller (30K) subunit proteins of several non-muscular tissues and cells was studied by testing immunological cross-reactivities. In addition to qualitative analyses by a conventional double immunodiffusion method, quantitative data were obtained, for the first time, by enzyme-linked immunosorbent assays using affinity-purified anticalpain I and anti-calpain II immunoglobulins. The enzyme sources included rat kidney, porcine kidney and erythrocytes, and human erythrocytes. It was concluded that the 30K subunits are immunologically almost indistinguishable between calpains, either I or II, not only from the same but also from different sources, while the 80K subunits of different origins are immunologically related to variable extents but always with discrimination between calpain I and calpain II. Similarity of the 30K subunit proteins and dissimilarity of the 80K counterparts were further substantiated by their chromatographic and electrophoretic behaviors.
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex; D002154:Calpain; D003429:Cross Reactions; D010450:Endopeptidases / Q000097:blood / Q000276:immunology / Q000302:isolation & purification*; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007106:Immune Sera; D005779:Immunodiffusion; D007668:Kidney / Q000201:enzymology; D046911:Macromolecular Substances; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D000936:Antigen-Antibody Complex; D007106:Immune Sera; D046911:Macromolecular Substances; D010450:Endopeptidases; D002154:Calpain