Conformational change following conversion of inactive rhinophrynin-33 to bioactive rhinophrynin-27 in the skin of the frog Rhinophrynus dorsalis

Paola Carta, JM Conlon, MA Scorciapino

Research output: Contribution to journalArticlepeer-review

Abstract

Skin secretions of the Mexican burrowing toad Rhinophrynus dorsalis (Rhinophrynidae) contain the proline-arginine-rich peptide, rhinophrynin-27 (RP-27; ELRLPEIARPVPEVLPARLPLPALPRN) with insulinotropic and immunomodulatory properties, together with a higher concentration of the biologically inactive form, rhinophrynin-33 (RP-33) that constitutes RP-27 extended from its C-terminus by the hexapeptide KMAKNQ. Determination of the conformation of RP-33 by NMR demonstrates that in both water and in a solvent that promotes protein folding (50% trifluoroethanol-water), the majority of the proline residues are found in a polyproline type II helical region. The peptide adopts a horseshoe (U-shaped) conformation with pronounced bends in the molecule of around 100°-120° at Glu and Arg . The hexapeptide extension adopts a α-helical conformation. When the hexapeptide is excised to generate RP-27, the molecule adopts an L-shaped conformation with a single bend at Glu . A search of protein sequence databases indicated the P-X-P-XXX-P-XXX-P-X-P motif found in RP-27 and RP-33 occurs in a number of proteins although its functional implications are unclear. The data suggest that RP-33 represents a biosynthetic precursor of RP-27 that is activated by a protease cleaving at a single lysine residue of the type previously identified in Xenopus laevis skin secretions. [Abstract copyright: Copyright © 2020 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.]
Original languageEnglish
Pages (from-to)162-168
Number of pages7
JournalBiochimie
Volume181
Early online date30 Dec 2020
DOIs
Publication statusPublished - 28 Feb 2021

Keywords

  • Amino acid pattern
  • Bioactive peptide
  • Immunomodulatory
  • Insulinotropic
  • Nuclear magnetic resonance
  • Xenopus

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