Chaperonin overexpression promotes genetic variation and enzyme evolution.
Most protein mutations, and mutations that alter protein functions in particular, undermine stability and are therefore deleterious. Chaperones, or heat-shock proteins, are often implicated in buffering mutations, and could thus facilitate the acquisition of neutral genetic diversity and the rate of adaptation. We examined the ability of the Escherichia coli GroEL/GroES chaperonins to buffer destabilizing and adaptive mutations. Here we show that mutational drifts performed in vitro with four different enzymes indicated that GroEL/GroES overexpression doubled the number of accumulating mutations, and promoted the folding of enzyme variants carrying mutations in the protein core and/or mutations with higher destabilizing effects (destabilization energies of >3.5 kcal mol(-)(1), on average, versus approximately 1 kcal mol(-)(1) in the absence of GroEL/GroES). The divergence of modified enzymatic specificity occurred much faster under GroEL/GroES overexpression, in terms of the number of adapted variants (>or=2-fold) and their improved specificity and activity (>or=10-fold). These results indicate that protein stability is a major constraint in protein evolution, and buffering mechanisms such as chaperonins are key in alleviating this constraint.
Tokuriki
Nobuhiko
N
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Tawfik
Dan S
DS
D018835:Chaperonin 10 / Q000235:genetics / Q000378:metabolism; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism; D018833:Chaperonins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D004950:Esterases / Q000378:metabolism; D019143:Evolution, Molecular; D015870:Gene Expression; D014644:Genetic Variation; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006801:Humans; D009154:Mutation; D055550:Protein Stability; D011549:Pseudomonas / Q000201:enzymology; D013379:Substrate Specificity
D018835:Chaperonin 10; D018834:Chaperonin 60; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D004950:Esterases; D018833:Chaperonins