Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Band 3 protein is a major erythrocyte transmembrane glycoprotein. We compared the degradation of band 3 protein by calpain I (a cytoplasmic, micromolar-Ca2(+)-requiring thiol proteinase) in the cells from old individuals (greater than 70 years old) to that in the cells from young ones (20-30 years old). In the young, little degradation of band 3 protein occurred in calpain-treated erythrocyte ghosts. In the old, significant band 3 protein degradation was found in erythrocyte ghosts treated similarly. The difference between young and old in the susceptibility of band 3 protein to calpain was retained in membrane vesicles (membranes stripped of peripheral proteins by NaOH) and in chymotrypsin-generated 60 kDa fragment (CH-60). The isolated N-terminal cytoplasmic 43 kDa fragment was degraded by calpain to a similar extent in old and in young. The separated 17 kDa membrane domain of the CH-60 and the trypsin-generated C-terminal 55 kDa membrane-spanning fragment were not degraded by calpain I in the young, nor in the old. Thus the N-terminal cytoplasmic domain is the domain degraded by calpain I. Enhanced sensitivity in the old is observed in intact band 3 protein and in CH-60, the isolated cytoplasmic domain being equally susceptible in young and old. The observed age-related enhanced sensitivity to calpain is consistent with the presence of modifications in band 3 protein and alterations in the association with the calpain-calpastatin system. Band 3 protein has several important functions, with modifications in the protein having implications for altered cell behaviour in the old individual.
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PMID:Band 3 protein degradation by calpain is enhanced in erythrocytes of old people. 201 84

Band 3, the anion channel protein of the human erythrocyte, is the major transmembrane glycoprotein of the erythrocyte membrane. The protein is distributed in a broad 88,000-98,000-dalton band on gel electrophoresis. Previous investigations have defined an NH2-terminal cytoplasmic domain and an adjacent membrane-spanning domain of the Band 3 molecule. The fragments containing these domains appear as discrete bands by sodium dodecyl sulfate polyacrylamide gel electrophoresis. A carboxyl-terminal fragment of the Band 3 molecule was generated by digestion with chymotrypsin at the external face of intact erythrocytes. This fragment appears as a broad band of Mr = 34,000-45,000. It has a site accessible to lactoperoxidase at the internal face of the membrane and must, therefore, span the membrane. Slices from different regions of the broad electrophoretic band of the carboxyl-terminal fragment of Band 3 all have identical peptide maps. The same is true of Band 3. Therefore, despite their heterogeneous appearance on gels, Band 3 and its proteolytic fragments are homogeneous polypeptides. This conclusion is supported by the finding of an unique NH2-terminal tetrapeptide sequence for one Band 3 fragment. The apparent heterogeneity of Band 3 and its carboxyl-terminal region may reflect variability of glycosylation or sodium dodecyl sulfate binding.
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PMID:The carboxyl-terminal domain of human erythrocyte band 3. Description, isolation, and location in the bilayer. 724 Feb 19