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Structural impact of proline mutations in the loop region of an ancestral membrane protein
Author(s) -
Nadeau Vincent G.,
Deber Charles M.
Publication year - 2016
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.22765
Subject(s) - chemistry , proline , loop (graph theory) , membrane protein , mutation , biophysics , membrane , biochemistry , gene , amino acid , biology , mathematics , combinatorics
The sodium ion‐translocating F 0 F 1 ATP synthase from the bacterium Ilyobacter tartaricus contains a highly stable rotor ring composed of 11 c subunits. The synthase subunit c—in effect an 89‐residue peptide that folds into a helical hairpin consisting of two membrane‐spanning helices and a cytoplasmic loop—was probed for the structural impact of a series of substitutions with the β‐turn‐inducing proline‐glycine couplet scanning the hairpin loop (residues 44‐51) of the I. tartaricus sequence. We found that a Pro residue in other than the wild type position 47 alters the gross secondary structure of subunit c from α‐helical to β‐sheet‐like, as well as changing its oligomeric ring structure, and its stability toward heat and trichloroacetic acid treatment. Such a Pro‐mediated structural switch in one of the first membrane proteins in life hints to a potential evolutionary connection between α‐helical and β‐sheet membrane proteins. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) : 37–42, 2016.