Relaxin

Relaxin is a protein hormone of about 6000 Da first described in 1926 by Frederick Hisaw.

The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1 (RLN1), 2 (RLN2) and 3 (RLN3), and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, INSL6 remain uncharacterised.

Synthesis

In the female, it is produced by the corpus luteum of the ovary, the breast and, during pregnancy, also by the placenta, chorion, and decidua.

In the male, it is produced in the prostate and is present in human semen.

Structure

Structurally, relaxin is a heterodimer of two peptide chains of 24 and 29 amino acids linked by disulfide bridges, and it appears related to insulin.

Relaxin is produced from its prohormone, "prorelaxin", by splitting off one additional peptide chain.

Function

In humans

In females relaxin is produced mainly by the corpus luteum, in both pregnant and nonpregnant females; it rises to a peak within approximately 14 days of ovulation, and then declines in the absence of pregnancy, resulting in menstruation ). During the first trimester of pregnancy, levels rise and additional relaxin is produced by the decidua. Relaxin's peak is reached during the 14 weeks of the first trimester and at delivery. It is known to mediate the hemodynamic changes that occur during pregnancy, such as increased cardiac output, increased renal blood flow, and increased arterial compliance. It also relaxes other pelvic ligaments. It is believed to soften the pubic symphysis.

Relaxin' with the Miles Davis Quintet

Relaxin' with the Miles Davis Quintet is an album recorded in 1956 by Miles Davis. Two sessions on 11 May 1956 and 26 October in the same year resulted in four albums—this one, Steamin' with the Miles Davis Quintet, Workin' with the Miles Davis Quintet and Cookin' with the Miles Davis Quintet. These four albums are considered to be among the best performances in the whole hard bop subgenre. The album was remastered by Rudy Van Gelder in 2005 for Prestige Records. This album includes dialogue snippets taken from the original master reel. It also emphasizes the Miles Davis' concentrated ballad-style playing with his medium-register trumpet.

Track listing

Relaxin-3

Relaxin-3 is a neuropeptide that was discovered in 2001, and which is highly conserved in species ranging from flies, fish, rodents and humans. Relaxin-3 is a member and ancestral gene of the relaxin family of peptides, which includes the namesake hormone relaxin (designated 'H2 relaxin' in humans) which mediates peripheral actions during pregnancy and which was found to relax the pelvic ligament in guinea pigs almost a century ago. The cognate receptor for relaxin-3 is the G-protein coupled receptor RXFP3 (relaxin family peptide 3 receptor), however relaxin-3 is pharmacologically able to also cross react with RXFP1 and RXFP3 (although the physiological relevance of such interactions, if they exist endogenously, are currently unknown).

Structure

Relaxin-3 consists of 51 amino acids in humans which are arranged into a two-chain structure (designated the A-chain and B-chain). There are three disulfide bonds (two interchain, one intrachain), with the residues that mediate binding to/activation of RXFP3 residing within the B-chain. At translation, pro-relaxin-3 also contains a C-chain (in between the A and B-chains) which is removed via protolytic cleavage to form the mature neuropeptide.