In mammalian cells vasodilator-stimulated phosphoprotein (VASP) is localized to focal adhesions and areas of dynamic membrane activity where it is thought to have a role in actinfilament assembly. The proteins responsible for recruiting VASP to these sites within the cell are not known. The bacterial protein ActA binds VASP via a proline-rich motif that is very similar to a sequence in the proline-rich region of the focal-adhesion protein vinculin. We have examined the ability of VASP, synthesized using an in vitro transcription/translation system, to bind to a series of vinculin peptides expressed as glutathione S-transferase fusion proteins, and have shown that it binds specifically to the proline-rich region in vinculin. Using immobilized peptides corresponding to the two proline-rich motifs within this domain, the VASP-binding site was localized to proline-rich motif-l (residues 839-850). Binding to this motif was not affected by the phosphorylation state of VASP. The C-terminal region of VASP, which is known to be important in targeting VASP to focal adhesions, was shown to be required for binding. These results identify vinculin as a VASP-binding protein likely to be important in recruiting VASP to focal adhesions and the cell membrane.

Islet autotransplantation offers a valuable addition to surgical resection of the pancreas, as a treatment for chronic pancreatitis; and even in cases in which insulin independence is not achieved, the potential beneficial effects of C-peptide make the procedure worthwhile.

Measurement of plasma levels of brain natriuretic peptide (BNP) has been used to assess left ventricular dysfunction and prognosis. Levels of the N-terminus of the precursor of BNP (NT-proBNP) have been reported to be elevated to a greater extent than BNP in left ventricular dysfunction. We have devised a non-radioactive sensitive and specific assay for NT-proBNP based on a competitive ligand binding principle. The chemiluminescent label 4-(2-succinimidyloxycarbonylethyl)phenyl-10-methylacridinium 9-carboxylate fluorosulphonate was used to label peptides representing domains in the middle and C-terminal sections of NT-proBNP. Assay of the C-terminal section of NT-proBNP (amino acids 65-76) in patients with proven left ventricular dysfunction [left ventricular wall motion index median 0.9 (range 0.3-1.4)] revealed elevated values [median 639 (386-911) fmol/ml] compared with normal controls [left ventricular wall motion index of 2 in all, NT-proBNP median 159 (120-245) fmol/ml, P<0.001]. Measurement of the middle section of NT-proBNP (amino acids 37-49) was not a discriminating test. It is thus possible to derivatize small peptides with a methyl acridinium label and preserve immunodetection with specific antibodies. Such methodology may allow non-radioactive immunoluminometric assays to be devised.

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