title: Protein quality control acts on folding intermediates to shape the effects of mutations on organismal fitness.
abstract: What are the molecular properties of proteins that fall on the radar of protein quality control (PQC)? Here we mutate the E. coli's gene encoding dihydrofolate reductase (DHFR) and replace it with bacterial orthologous genes to determine how components of PQC modulate fitness effects of these genetic changes. We find that chaperonins GroEL/ES and protease Lon compete for binding to molten globule intermediate of DHFR, resulting in a peculiar symmetry in their action: overexpression of GroEL/ES and deletion of Lon both restore growth of deleterious DHFR mutants and most of the slow-growing orthologous DHFR strains. Kinetic steady-state modeling predicts and experimentation verifies that mutations affect fitness by shifting the flux balance in cellular milieu between protein production, folding, and degradation orchestrated by PQC through the interaction with folding intermediates.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
authors.forename: Shimon
authors.initials: S
authors.lastname: Bershtein
authors.forename: Wanmeng
authors.initials: W
authors.lastname: Mu
authors.forename: Adrian W R
authors.initials: AW
authors.lastname: Serohijos
authors.forename: Jingwen
authors.initials: J
authors.lastname: Zhou
authors.forename: Eugene I
authors.initials: EI
authors.lastname: Shakhnovich
mesh_terms: D000465:Algorithms; D020816:Amino Acid Motifs; D001483:Base Sequence; D018835:Chaperonin 10 / Q000235:genetics / Q000378:metabolism; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D055786:Gene Knockout Techniques; D056084:Genetic Fitness; D006706:Homeostasis; D007700:Kinetics; D050296:Microbial Viability; D008954:Models, Biological; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D049070:Protease La / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D017510:Protein Folding; D059748:Proteolysis; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D029968:Escherichia coli Proteins; D013762:Tetrahydrofolate Dehydrogenase; C483567:Lon protein, E coli; D049070:Protease La