Expression of spasmolysin (FIM-A.1): an integumentary mucin from Xenopus laevis
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In the past, a unique type of precursor for a secretory protein was discovered. It contains a central repetitive domain rich in threonine residues and terminal cysteine-rich domains. Due to striking homologies of these terminal domains with pancreatic spasmolytic polypeptide, originally the name "prepro-spasmolysin" was proposed. Here we show that the mature protein has a MW of about 130 kDa, consisting of about 70% carbohydrate and 30% protein. Similar O-linked glycoproteins have been found in mucins from human intestine. For this and numerous other reasons we decided to rename this glycoprotein "frog integumentary mucin A.1" (FIM-A.1). Furthermore, analysis of the protein with specific antibodies against the predicted C-terminal end indicates that FIM-A.1 is probably not processed at pairs of basic residues. In situ hybridization as well as immunofluorescence studies revealed that FIM-A.1 is expressed and stored exclusively in mature mucous glands of Xenopus laevis skin. Only cone cells at the proximal part of these glands do not synthesize FIM-A.1. In contrast, all other physiologically active peptides from X. laevis skin investigated so far are synthesized in granular glands. A hypothetical function of FIMs for defense against microbial infections is discussed.
Originalsprog | Engelsk |
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Tidsskrift | Experimental Cell Research |
Vol/bind | 189 |
Udgave nummer | 2 |
Sider (fra-til) | 157-62 |
Antal sider | 6 |
ISSN | 0014-4827 |
DOI | |
Status | Udgivet - aug. 1990 |
ID: 347886198