Relaxin-like bioactivity of ovine Insulin 3 (INSL3) analogues.

Relaxin is an insulin-like peptide consisting of two separate chains (A and B) joined by two inter- and one intrachain disulfide bonds. Binding to its receptor requires an Arg-X-X-X-Arg-X-X-Ile motif in the B-chain. A related member of the insulin superfamily, INSL3, has a tertiary structure that is predicted to be similar to relaxin.

Structural requirements for the interaction of sheep insulin-like factor 3 with relaxin receptors in rat atria.

Relaxin is a peptide with various reproductive and nonreproductive functions. The site for the peptide-receptor interaction contains two arginines (Arg) and an isoleucine (Ile) or valine (Val) residue in the B-chain with a configuration of -Arg-X-X-X-Arg-X-X-Ile/Val-X-. The sheep insulin-like peptide 3 (INSL3), a structural homologue of relaxin, also contains the n, n+4 arginines in the B-chain but they are displaced towards the carboxyl terminus by four residues (-X-X-X-X-Arg-X-X-Val-Arg-).

Purification and characterization of relaxin from the tammar wallaby (Macropus eugenii): bioactivity and expression in the corpus luteum.

The objective of this study was to isolate and purify prorelaxin or mature relaxin from the tammar wallaby corpus luteum (CL), determine their structure and bioactivity, and test the hypothesis that enzymatic cleavage of prorelaxin occurs in late gestation. Tammar relaxin peptides were extracted from pooled corpora lutea of late pregnant tammars using a combination of HPLC methods, and they were identified using Western blotting with a human (H2) relaxin antisera and matrix-assisted laser desorption ionization time of flight mass spectrometry. Although no prorelaxin was identified, multiple 6-kDa peptides were detected, which corresponded to the predicted mature tammar relaxin amino acid sequence, with an A chain of 24 amino acids, and different B chain lengths of 28, 29, 30, and 32 amino acids.

Human relaxin gene 3 (H3) and the equivalent mouse relaxin (M3) gene. Novel members of the relaxin peptide family.

We have identified a novel human relaxin gene, designated H3 relaxin, and an equivalent relaxin gene in the mouse from the Celera Genomics data base. Both genes encode a putative prohormone sequence incorporating the classic two-chain, three cysteine-bonded structure of the relaxin/insulin family and, importantly, contain the RXXXRXX(I/V) motif in the B-chain that is essential for relaxin receptor binding. A peptide derived from the likely proteolytic processing of the H3 relaxin prohormone sequence was synthesized and found to possess relaxin activity in bioassays utilizing the human monocytic cell line, THP-1, that expresses the relaxin receptor.