Isolation and characterization of two glycoproteins from the salivary glands of isoproterenol-treated hamsters
Abstract
Isoproterenol induces several proline-rich phosphoproteins in the hamster parotid gland (Mehansho, H., Ann, D. K., Butler, L. G., Rogler, J. and Carlson, D. M. J. Biol. Chem. 262, 12344-12350). One of these phosphoproteins is also glycosylated and appears to be regulated in a dose-dependent manner. This phosphoglycoprotein (PGP89) has an apparent molecular weight of 89,000 on SDS-PAGE. Purification of PGP89 was greatly assisted by its solubility in 10% trichloroacetic acid which was followed by a combination of gel filtration and ion exchange chromatography. Sequence analysis showed that the amino-terminal of PGP89 is blocked. Clostripain digestion yielded one major glycopeptide which had the sequence H G N Q T Q P R P P R P D. This sequence of the glycopeptide of PGP89 is almost the same as that found for SGP158 (Mehansho, H., and Carlson, D. M. (1983) J. Biol. Chem. 258 6616-6620) D G N Q T Q P R P P H P. Antibodies made against deglycosylated rat SGP158 cross-react with both the native and deglycosylated hamster PGP89. Isoproterenol also induces proline-rich proteins in the submandibular glands of hamsters. One of these proteins is a glycoprotein (SGP180) with an apparent molecular weight on SDS-PAGE of 180,000. Unlike the other proline-rich proteins induced by isoproterenol there is a high basal level of SGP180. Isoproterenol results in at most a three-fold induction. Like the PRPs SGP180 is soluble in 10% trichloroacetic acid and contains low amount of aromatics and sulfur containing amino acids, but unlike the PRPs the proline content is low (16%). SGP180 which closely resembles mucin glycoproteins is high in hydroxy-amino acids, (threonine 50%) and contains 60% carbohydrate which is O-linked. The carbohydrate moiety is like that of ovine submaxillary gland mucin, N-acetylneuraminic acid linked to N-acetylgalactosamine. The presence of sialic acid makes the glycoprotein resistant to proteases, a factor that was exploited in its purification.
Degree
Ph.D.
Advisors
Carlson, Purdue University.
Subject Area
Biochemistry
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