Genes 2011, 2(3), 608-626; doi:10.3390/genes2030608
Article

Protein Folding Absent Selection

1,* email, 2email, 3email and 1email
Received: 10 July 2011; in revised form: 5 August 2011 / Accepted: 11 August 2011 / Published: 16 August 2011
(This article belongs to the Special Issue Evolution and Structure of Proteins and Proteomes)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: Biological proteins are known to fold into specific 3D conformations. However, the fundamental question has remained: Do they fold because they are biological, and evolution has selected sequences which fold? Or is folding a common trait, widespread throughout sequence space? To address this question arbitrary, unevolved, random-sequence proteins were examined for structural features found in folded, biological proteins. Libraries of long (71 residue), random-sequence polypeptides, with ensemble amino acid composition near the mean for natural globular proteins, were expressed as cleavable fusions with ubiquitin. The structural properties of both the purified pools and individual isolates were then probed using circular dichroism, fluorescence emission, and fluorescence quenching techniques. Despite this necessarily sparse “sampling” of sequence space, structural properties that define globular biological proteins, namely collapsed conformations, secondary structure, and cooperative unfolding, were found to be prevalent among unevolved sequences. Thus, for polypeptides the size of small proteins, natural selection is not necessary to account for the compact and cooperative folded states observed in nature.
Keywords: protein folding; evolution; sequence space
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MDPI and ACS Style

LaBean, T.H.; Butt, T.R.; Kauffman, S.A.; Schultes, E.A. Protein Folding Absent Selection. Genes 2011, 2, 608-626.

AMA Style

LaBean TH, Butt TR, Kauffman SA, Schultes EA. Protein Folding Absent Selection. Genes. 2011; 2(3):608-626.

Chicago/Turabian Style

LaBean, Thomas H.; Butt, Tauseef R.; Kauffman, Stuart A.; Schultes, Erik A. 2011. "Protein Folding Absent Selection." Genes 2, no. 3: 608-626.

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