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

The effects of human red cell glycophorin A (GPA) on the expression of the human erythrocyte anion transporter (band 3, AE1) has been examined in Xenopus oocytes. The coexpression of GPA with band 3 increased stilbene disulfonate-sensitive chloride transport into the oocytes. The effect of GPA was particularly noticeable at low band 3 concentrations and less marked at high band 3 cRNA concentrations. The enhancement of chloride transport was specific to GPA and was not observed when either glycophorin B or glycophorin C was coexpressed with band 3. Immunoprecipitations of whole oocyte homogenates showed the amount of band 3 synthesized was not affected by GPA at subsaturating cRNA concentrations. More band 3 was detected at the oocyte surface by immunoprecipitation when GPA was also expressed. Chymotrypsin treatment of intact oocytes was also used to assess surface band 3 and greater cleavage of band 3 by chymotrypsin was observed when GPA was present. Band 3 synthesis and assembly into canine pancreatic microsomes in the reticulocyte cell-free translation system was not altered by cotranslation of GPA. We suggest that GPA facilitates the translocation of band 3 to the plasma membrane at some point during band 3 biosynthesis in Xenopus oocytes. However, GPA is not essential for the expression of band 3 in red cells, since GPA-deficient individuals have apparently normal levels of band 3. Other GPA-independent mechanisms must also allow translocation of band 3 to the surface membrane in erythroid cells and oocytes. GPA may affect the rate of accumulation of band 3 at the cell surface, rather than the final level in the plasma membrane.
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PMID:Glycophorin A facilitates the expression of human band 3-mediated anion transport in Xenopus oocytes. 138 95

Immunological analogues of band 3, the anion transporter, have been identified in all cells that have been studied, including both isolated neurons and neurons of the central nervous system. We studied band 3 structural/functional relationships in a family in which the proposita has a serious, progressive, genetic neurologic disorder with acanthocytosis (choreoacanthocytosis). Biochemical studies of erythrocytes from the proposita, her mother and brother revealed that maximal sulfate transport velocity (Vmax) and sodium transport were increased, glucose efflux was decreased. Ankyrin binding was normal. Immunologic studies revealed increased IgG binding to middle-aged cells of the proposita and her brother, binding of antibodies to aged band 3 to a distinct region of band 3 in erythrocyte membranes in immunoblots, and binding of choreoacanthocytosis sera IgG to erythroid and brain band 3 and synthetic peptides of band 3 in immunoblots. Antibodies to neural and, to a lesser extent, renal tissue were observed in choreoacanthocytosis sera. These antibodies appear to have a band 3 specificity. Monoclonal antibodies to 150 residues of the carboxyl terminus of band 3 stained two band 3 fragments in immunoblots of chymotrypsin-digested membranes that are not present in control cells. This suggests that band 3 is altered in this autosomal recessive neurologic disorder. In addition, these monoclonal antibodies stained five band 3 breakdown products in membranes of untreated red cells in both control and choreoacanthocytosis cells. The possibility that a disturbance of some function of band 3 may contribute to the neurologic abnormalities in affected individuals is intriguing. This is the first evidence for abnormalities of membrane transport in the neurologic disorder known as choreoacanthocytosis.
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PMID:Membrane protein band 3 alteration associated with neurologic disease and tissue-reactive antibodies. 238 5

Band 3, the erythrocyte anion transporter, has been shown to transfer between human erythrocytes and sonicated vesicles (Newton, A. C., Cook, S. L., and Huestis, W. H. (1983) Biochemistry 22, 6110-6117). Functional band 3 becomes associated with dimyristoylphosphatidylcholine vesicles incubated with human red blood cells. Proteolytic degradation patterns reveal that the transporter is transferred to the vesicles in native orientation. In erythrocytes, native band 3 is degraded on the exoplasmic membrane face by chymotrypsin and on the cytoplasmic surface by trypsin (Cabantchik, Z. I., and Rothstein, A. (1974) J. Membr. Biol. 15, 227-248; Jennings, M. L., Anderson, M. P., and Monaghan, R. (1986) J. Biol. Chem. 261, 9002-9010). Band 3 in intact protein-vesicle complexes is degraded by exogenous chymotrypsin but not by trypsin. In contrast, trypsin entrapped in the lumen of the vesicles proteolyses the vesicle-bound band 3 quantitatively. Band 3 remaining in the membranes of vesicle-treated cells and in cell fragments is not degraded detectably by vesicle-entrapped trypsin. These observations indicate that band 3 is unlikely to transfer between cell and vesicle membranes via a water-soluble form or to adhere nonspecifically to the vesicle surface; the aqueous contents of vesicles and cells (or membrane fragments) are not pooled during cell-vesicle incubations, hence no cell-vesicle fusion occurs; and the band 3 associated with the sonicated vesicle fraction is inserted in the vesicle bilayer in native orientation, with its cytoplasmic segment contacting the aqueous contents of the vesicle lumen.
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PMID:Intermembrane protein transfer. Band 3, the erythrocyte anion transporter, transfers in native orientation from human red blood cells into the bilayer of phospholipid vesicles. 378 18