Solution Structure of Human Proguanylin

Abstract

The endogenous ligand of guanylyl cyclase C, guanylin, is produced as the 94-amino-acid prohormone proguanylin, with the hormone guanylin located at the COOH terminus of the prohormone. The solution structure of proguanylin adopts a new protein fold and consists of a three-helix bundle, a small three-stranded ␤-sheet of two NH 2 -terminal strands and one COOHterminal strand, and an unstructured linker region. The sequence corresponding to guanylin is fixed in its bioactive topology and is involved in interactions with the NH 2 -terminal ␤-hairpin: the hormone region (residues 80 -94) partly wraps around the first 4 NH 2 -terminal residues that thereby shield parts of the hormone surface. These interactions provide an explanation for the negligible bioactivity of the prohormone as well as the important role of the NH 2 -terminal residues in the disulfide-coupled folding of proguanylin. Since the ligand binding region of guanylyl cyclase C is predicted to be located around an exposed ␤-strand, the intramolecular interactions observed between guanylin and its prosequence may be comparable with the guanylin/receptor interaction.

Prosequence-Mediated Disulfide Coupled Folding of the Peptide Hormones Guanylin and Uroguanylin

“…Additionally, it was shown for prouroguanylin that the hormone part exclusively adopts the A-form topology after digestion of the prohormone and release of the mature hormone region [10], which is the same as observed in the proguanylin structure (Fig. 3 B) [27]. Based on these findings it has been suggested that prouroguanylin adopts a fold similar to that of proguanylin [27], allowing comparative modelling of the prouroguanylin structure (Fig.…”

“…3 B) [27]. Based on these findings it has been suggested that prouroguanylin adopts a fold similar to that of proguanylin [27], allowing comparative modelling of the prouroguanylin structure (Fig. 3 C).…”

“…For this mutant protein, predominantely uroguanylin with the native fold was obtained after oxidative folding [11], implying rather important backbone/backbone interactions than a role of the side chain of Tyr2 during the folding process. Indeed, Lauber et al [27] have shown that the very NH 2 -terminal part of the prosequence and the hormone region of the closely related guanylin prohormone interact via backbone/backbone interactions with each other (see below). The same kind of interactions can also be assumed for prouroguanylin as discussed below.…”

“…The recent determination of the solution structure of proguanylin [27] revealed a globularly folded protein composed of a three helix bundle and a small triple-stranded antiparallel β-sheet of two NH 2 -terminal strands and one strand of the very COOH-terminus (Fig. 3 A).…”

Characterization of Immunological Cross-Reactivity between Enterotoxigenic Escherichia coli Heat-Stable Toxin and Human Guanylin and Uroguanylin

“…The proforms of guanylin and uroguanylin were chosen as coatings for guanylin and uroguanylin competitive ELISAs to ensure binding and competition of A-form-specific antibodies (48). The cDNA sequences of proguanylin (IMAGE ID 100062076) and prouroguanylin (IMAGE ID 7939624; http://www.imageconsortium.org) were cloned into the pSXG vector (49) as GST fusions.…”