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Characterization of two potentially universal turn motifs that shape the repeated five‐residues fold—Crystal structure of a lumenal pentapeptide repeat protein from Cyanothece 51142
Author(s) -
Buchko Garry W.,
Ni Shuisong,
Robinson Howard,
Welsh Eric A.,
Pakrasi Himadri B.,
Kennedy Michael A.
Publication year - 2006
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.062407506
Subject(s) - pentapeptide repeat , tandem repeat , biology , structural motif , protein structure , biochemistry , stereochemistry , chemistry , peptide , genome , gene
Abstract The genome of the diurnal cyanobacterium Cyanothece sp. PCC 51142 has recently been sequenced and observed to contain 35 pentapeptide repeat proteins (PRPs). These proteins, while present throughout the prokaryotic and eukaryotic kingdoms, are most abundant in cyanobacteria. The sheer number of PRPs in cyanobacteria coupled with their predicted location in every cellular compartment argues for important, yet unknown, physiological and biochemical functions. To gain biochemical insights, the crystal structure for Rfr32, a 167‐residue PRP with an N‐terminal 29‐residue signal peptide, was determined at 2.1 Å resolution. The structure is dominated by 21 tandem pentapeptide repeats that fold into a right‐handed quadrilateral β‐helix, or Rfr‐fold, as observed for the tandem pentapeptide repeats in the only other PRP structure, the mycobacterial fluoroquinoline resistance protein MfpA from Mycobacterium tuberculosis . Sitting on top of the Rfr‐fold are two short, antiparallel α‐helices, bridged with a disulfide bond, that perhaps prevent edge‐to‐edge aggregation at the C terminus. Analysis of the main‐chain (Φ,Ψ) dihedral orientations for the pentapeptide repeats in Rfr32 and MfpA makes it possible to recognize the structural details for the two distinct types of four‐residue turns adopted by the pentapeptide repeats in the Rfr‐fold. These turns, labeled type II and type IV β‐turns, may be universal motifs that shape the Rfr‐fold in all PRPs.