title: Evolution of Protein Quaternary Structure in Response to Selective Pressure for Increased Thermostability.
abstract: Oligomerization has been suggested to be an important mechanism for increasing or maintaining the thermostability of proteins. Although it is evident that protein-protein contacts can result in substantial stabilization in many extant proteins, evidence for evolutionary selection for oligomerization is largely indirect and little is understood of the early steps in the evolution of oligomers. A laboratory-directed evolution experiment that selected for increased thermostability in the αE7 carboxylesterase from the Australian sheep blowfly, Lucilia cuprina, resulted in a thermostable variant, LcαE7-4a, that displayed increased levels of dimeric and tetrameric quaternary structure. A trade-off between activity and thermostability was made during the evolution of thermostability, with the higher-order oligomeric species displaying the greatest thermostability and lowest catalytic activity. Analysis of monomeric and dimeric LcαE7-4a crystal structures revealed that only one of the oligomerization-inducing mutations was located at a potential protein-protein interface. This work demonstrates that by imposing a selective pressure demanding greater thermostability, mutations can lead to increased oligomerization and stabilization, providing support for the hypothesis that oligomerization is a viable evolutionary strategy for protein stabilization.
authors.affiliation: Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Fraser
authors.affiliation: Commonwealth Scientific and Industrial Research Organization, Land and Water Flagship, Canberra, ACT 0200, Australia.
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Liu
authors.affiliation: Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Mabbitt
authors.affiliation: Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
authors.forename: Galen J
authors.initials: GJ
authors.lastname: Correy
authors.affiliation: Commonwealth Scientific and Industrial Research Organization, Land and Water Flagship, Canberra, ACT 0200, Australia.
authors.forename: Chris W
authors.initials: CW
authors.lastname: Coppin
authors.affiliation: Institut de Biologie Structurale, Commissariat a l'Energie Atomique, F-38027 Grenoble, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Lethier
authors.affiliation: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Perugini
authors.affiliation: Cell Signalling and Cell Death Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Melbourne, VIC 3050, Australia.
authors.forename: James M
authors.initials: JM
authors.lastname: Murphy
authors.affiliation: Commonwealth Scientific and Industrial Research Organization, Land and Water Flagship, Canberra, ACT 0200, Australia.
authors.forename: John G
authors.initials: JG
authors.lastname: Oakeshott
authors.affiliation: Institut de Biologie Structurale, Commissariat a l'Energie Atomique, F-38027 Grenoble, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Weik
authors.affiliation: Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia. Electronic address: cjackson@rsc.anu.edu.au.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Jackson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001315:Australia; D005075:Biological Evolution; D009154:Mutation / Q000235:genetics; D055503:Protein Multimerization / Q000235:genetics; D020836:Protein Structure, Quaternary; D011506:Proteins / Q000235:genetics*; D016415:Sequence Alignment / Q000379:methods; D012756:Sheep / Q000235:genetics
chemical_list: D011506:Proteins
keywords: carboxylesterase; directed evolution; interface; oligomerization; thermostability