The B1-immunoreactive proteins (B1-IPs) are major secretory products of rat submandibular gland acinar-cell progenitors, and are also produced by neonatal and adult rat sublingual and parotid glands. In order to characterize the B1-IPs, we have previously isolated cDNA clones encoding rat parotid secretory protein (PSP; the predominant parotid B1-IP) and the related clone ZZ3, which is developmentally regulated in the neonatal submandibular gland. The remainder of the B1-IPs were uncharacterized. This report demonstrates that all of the B1-IPs are derived from the PSP and ZZ3 transcripts. Molecular cloning and Western-blot analyses using PSP- and ZZ3-specific antisera show that, of the B1-IPs, only PSP and neonatal submandibular gland protein A (SMGA) are products of the Psp gene. This finding corrects our previous assertion that SMGA is derived from ZZ3. Neonatal submandibular gland proteins B1 and B2, as well as apparent Mr 26000-28000 and Mr 18000-20000 forms in submandibular, sublingual and parotid glands, are derived from the gene encoding ZZ3 by differential N-glycosylation and by proteolytic cleavage. The apparent Mr 18000-20000 proteolytic products are significant in secretion product collected in vitro, but rare in gland homogenate and submandibular/sublingual saliva. The gene encoding ZZ3 has been named Smgb. Psp and Smgb are regulated similarly in the developing submandibular gland, but differently in the sublingual and parotid glands. The expression pattern of Psp is conserved between rat and mouse. However, no evidence for proteins derived from an Smgb-like gene was observed in neonatal mouse submandibular or sublingual glands.
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February 1998
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Research Article|
February 15 1998
Characterization of the rat salivary-gland B1-immunoreactive proteins
Lily MIRELS;
Lily MIRELS
1
*Biology Department, University of California, San Diego, La Jolla, CA 92093-0347, U.S.A.
1To whom correspondence should be addressed. Present address: Department of Molecular and Cell Biology, Division of Genetics, 401 Barker Hall, University of California, Berkeley, CA 94720-3204, U.S.A.
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J. Abigail MIRANDA;
J. Abigail MIRANDA
*Biology Department, University of California, San Diego, La Jolla, CA 92093-0347, U.S.A.
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D. William BALL
D. William BALL
1
*Biology Department, University of California, San Diego, La Jolla, CA 92093-0347, U.S.A.
†Department of Anatomy and the Howard University Cancer Center, Howard University College of Medicine, Washington, DC 20059, U.S.A.
1To whom correspondence should be addressed. Present address: Department of Molecular and Cell Biology, Division of Genetics, 401 Barker Hall, University of California, Berkeley, CA 94720-3204, U.S.A.
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Publisher: Portland Press Ltd
Received:
March 10 1997
Revision Received:
September 30 1997
Accepted:
November 03 1997
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 330 (1): 437–444.
Article history
Received:
March 10 1997
Revision Received:
September 30 1997
Accepted:
November 03 1997
Citation
Lily MIRELS, J. Abigail MIRANDA, D. William BALL; Characterization of the rat salivary-gland B1-immunoreactive proteins. Biochem J 15 February 1998; 330 (1): 437–444. doi: https://doi.org/10.1042/bj3300437
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