title: Physiological effects of unassembled chaperonin Cct subunits in the yeast Saccharomyces cerevisiae.
abstract: Eukaryotic chaperonins, the Cct complexes, are assembled into two rings, each of which is composed of a stoichiometric array of eight different subunits, which are denoted Cct1p-Cct8p. Overexpression of a single CCT gene in Saccharomyces cerevisiae causes an increase of the corresponding Cct subunit, but not of the Cct complex. Nevertheless, overexpression of certain Cct subunits, especially CCT6, suppresses a wide range of abnormal phenotypes, including those caused by the diverse types of conditional mutations tor2-21, lst8-2 and rsp5-9 and those caused by the concomitant overexpression of Sit4p and Sap155p. The examination of 73 altered forms of Cct6p revealed that the cct6-24 mutation, containing GDGTT --> AAAAA replacements of the conserved ATP-binding motif, was unable to suppress any of these traits, although the cct6-24 allele was completely functional for growth. These results provide evidence for functional differences among Cct subunits and for physiological properties of unassembled subunits. We suggest that the suppression is due to the competition of specific Cct subunits for activities that normally modify various cellular components. Furthermore, we also suggest that the Cct subunits can act as suppressors only in certain states, such as when associated with ATP.
authors.affiliation: Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA.
authors.forename: M Anaul
authors.initials: MA
authors.lastname: Kabir
authors.forename: Joanna
authors.initials: J
authors.lastname: Kaminska
authors.forename: George B
authors.initials: GB
authors.lastname: Segel
authors.forename: Gabor
authors.initials: G
authors.lastname: Bethlendy
authors.forename: Paul
authors.initials: P
authors.lastname: Lin
authors.forename: Flavio
authors.initials: F
authors.lastname: Della Seta
authors.forename: Casey
authors.initials: C
authors.lastname: Blegen
authors.forename: Kristine M
authors.initials: KM
authors.lastname: Swiderek
authors.forename: Teresa
authors.initials: T
authors.lastname: Zoładek
authors.forename: Kim T
authors.initials: KT
authors.lastname: Arndt
authors.forename: Fred
authors.initials: F
authors.lastname: Sherman
mesh_terms: D056404:Chaperonin Containing TCP-1; D018833:Chaperonins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D015966:Gene Expression Regulation, Fungal; D013058:Mass Spectrometry; D008954:Models, Biological; D010957:Plasmids; D016133:Polymerase Chain Reaction; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins