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Solution structures and backbone dynamics of the ribosomal protein S6 and its permutant P 54‐55
Author(s) -
Öhman Anders,
Öman Tommy,
Oliveberg Mikael
Publication year - 2010
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 - 10.1002/pro.298
Subject(s) - crystallography , thermus thermophilus , antiparallel (mathematics) , crystal structure , chemistry , ribosomal protein , protein structure , molecular dynamics , physics , ribosome , rna , biochemistry , computational chemistry , escherichia coli , quantum mechanics , magnetic field , gene
The ribosomal protein S6 from Thermus thermophilus has served as a model system for the study of protein folding, especially for understanding the effects of circular permutations of secondary structure elements. This study presents the structure of a permutant protein, the 96‐residue P 54‐55 , and the structure of its 101‐residue parent protein S6 wt in solution. The data also characterizes the effects of circular permutation on the backbone dynamics of S6. Consistent with crystallographic data on S6 wt , the overall solution structures of both P 54‐55 and S6 wt show a β‐sheet of four antiparallel β‐strands with two α‐helices packed on one side of the sheet. In clear contrast to the crystal data, however, the solution structure of S6 wt reveals a disordered loop in the region between β‐strands 2 and 3 (Leu43‐Phe60) instead of a well‐ordered stretch and associated hydrophobic mini‐core observed in the crystal structure. Moreover, the data for P 54‐55 show that the joined wild‐type N‐ and C‐terminals form a dynamically robust stretch with a hairpin structure that complies with the in silico design. Taken together, the results explain why the loop region of the S6 wt structure is relatively insensitive to mutational perturbations, and why P 54‐55 is more stable than S6 wt : the permutant incision at Lys54‐Asp55 is energetically neutral by being located in an already disordered loop whereas the new hairpin between the wild‐type N‐ and C‐termini is stabilizing.