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Identification of a “glycine‐loop”‐like coiled structure in the 34 AA Pro,Gly,Met repeat domain of the biomineral‐associated protein, PM27
Author(s) -
Wustman Brandon A.,
Santos Rudolpho,
Zhang Bo,
Evans John Spencer
Publication year - 2002
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10274
Subject(s) - spicule , chemistry , peptide , sponge spicule , peptide sequence , protein structure , coiled coil , biophysics , crystallography , biochemistry , biology , gene , anatomy
Fracture resistance in biomineralized structures has been linked to the presence of proteins, some of which possess sequences that are associated with elastic behavior. One such protein superfamily, the Pro,Gly‐rich sea urchin intracrystalline spicule matrix proteins, form protein–protein supramolecular assemblies that modify the microstructure and fracture‐resistant properties of the calcium carbonate mineral phase within embryonic sea urchin spicules and adult sea urchin spines. In this report, we detail the identification of a repetitive keratin‐like “glycine‐loop”‐ or coil‐like structure within the 34‐AA (AA: amino acid) N‐terminal domain, (PGMG) 8 PG, of the spicule matrix protein, PM27. The identification of this repetitive structural motif was accomplished using two capped model peptides: a 9‐AA sequence, GPGMGPGMG, and a 34‐AA peptide representing the entire motif. Using CD, NMR spectrometry, and molecular dynamics simulated annealing/minimization simulations, we have determined that the 9‐AA model peptide adopts a loop‐like structure at pH 7.4. The structure of the 34‐AA polypeptide resembles a coil structure consisting of repeating loop motifs that do not exhibit long‐range ordering. Given that loop structures have been associated with protein elastic behavior and protein motion, it is plausible that the 34‐AA Pro,Gly,Met repeat sequence motif in PM27 represents a putative elastic or mobile domain. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 362–372, 2002