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Characterization of Dopuin, a Polypeptide with Special Residue Distributions

1997; Wiley; Volume: 249; Issue: 2 Linguagem: Inglês

10.1111/j.1432-1033.1997.t01-2-00518.x

1432-1033

Zheng‐wang Chen, Tomas Bergman, Claes‐Göran Östenson, Suad Efendić, Viktor Mutt, Hans Jörnvall,

Cell Adhesion Molecules Research

A 62‐residue polypeptide, dopuin, has been isolated from pig small intestine. It is distinguished by an N‐terminal part with a high content of proline (7 in a 26‐residue segment), a C‐terminal part with a high proportion of histidine (3 in a 9‐residue segment), and six half‐cystine residues in three intrachain disulphide bridges (connecting positions 22–25, 23–54 and 35–44). The Cys and Pro distributions suggest a tight and special conformation. In contrast to PEC‐60 and somatostatin, it has no established inhibitory effect on insulin secretion. At 10 nM concentration, a weak inhibitory tendency is less than half of that of the other two peptides. Like gastrointestinal trefoil peptides, dopuin has three disulphide bridges, Ala‐Pro segments, and many charged residues, but they are differently distributed and dopuin belongs to a separate, apparently novel family. However, dopuin is similar to a peptide corresponding to an expressed‐sequence‐tag cDNA of human fetal liver and spleen, establishing the nature of the mature form of the product of this cDNA, and showing a general tissue, age, and species distribution of this peptide. A truncated form of vimentin, composed of its C‐terminal 37 residues, vimentin‐C37, was also purified and structurally characterized. These two peptides increase the complexity of known intestinal polypeptides and at least dopuin has properties compatible with specific biofunctions.