title: Characterization of polypeptides serologically and structurally related to hexosaminidase in cultured fibroblasts.
abstract: Human fibroblasts synthesize several polypeptides that assort into the various forms of hexosaminidase (hex). We report here the occurrence of three newly identified, hexosaminidase-related polypeptides resolved by sodium dodecyl sulfate-poly-acrylamide gel electrophoresis of immunoprecipitates from [35S]methionine-labeled cell extracts. These polypeptides, called band 2 (75,000), band 3 (70,000), and band 4 (63,000), were immunoprecipitated by an antiserum specific to placental hex I2. They are distinct from pre-alpha- (60,000) and pre-beta- (58,000) precursor polypeptides and the alpha- (56,000), beta a- (27,000), and beta b- (27,000) polypeptides of the mature hex A (alpha beta a beta b) and hex B (2[beta a beta b]). When fibroblast extracts were chromatographed on DEAE-Sepharose, bands 2, 3, and 4 were eluted together in fractions before hex A, in a position characteristic of serum and placental hex I2 and serum hex P. This suggests that bands 2, 3, and 4 might represent the polypeptides of a fibroblast hex I. The analysis of partial proteolytic digests of the radioactively labeled polypeptides revealed that bands 2 and 3, pre-beta, and beta a had several peptides in common, suggesting that they are structurally related to each other. However, bands 2, 3, and 4 were present in extracts of Tay-Sachs (pre-alpha and alpha deficiency) and Sandhoff cells (pre-beta, beta a, and beta b deficiency) and appeared later than pre-beta in pulse-chase experiments. These results suggest that bands 2 and 3 occur independently of pre-beta and beta a and are probably specified by different mRNA, whether from the same gene or distinct but homologous genes.
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000032:analysis; D055598:Chemical Phenomena; D011232:Chemical Precipitation; D002621:Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D006596:Hexosaminidases / Q000032:analysis* / Q000096:biosynthesis / Q000276:immunology; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis*; D011247:Pregnancy; D011817:Rabbits; D012497:Sandhoff Disease / Q000201:enzymology / Q000235:genetics; D013661:Tay-Sachs Disease / Q000201:enzymology / Q000235:genetics
chemical_list: D000936:Antigen-Antibody Complex; D007106:Immune Sera; D010455:Peptides; D006596:Hexosaminidases