Structure-function relationships in yeast tubulins.
A comprehensive set of clustered charged-to-alanine mutations was generated that systematically alter TUB1, the major alpha-tubulin gene of Saccharomyces cerevisiae. A variety of phenotypes were observed, including supersensitivity and resistance to the microtubule-destabilizing drug benomyl, lethality, and cold- and temperature-sensitive lethality. Many of the most benomyl-sensitive tub1 alleles were synthetically lethal in combination with tub3Delta, supporting the idea that benomyl supersensitivity is a rough measure of microtubule instability and/or insufficiency in the amount of alpha-tubulin. The systematic tub1 mutations were placed, along with the comparable set of tub2 mutations previously described, onto a model of the yeast alpha-beta-tubulin dimer based on the three-dimensional structure of bovine tubulin. The modeling revealed a potential site for binding of benomyl in the core of beta-tubulin. Residues whose mutation causes cold sensitivity were concentrated at the lateral and longitudinal interfaces between adjacent subunits. Residues that affect binding of the microtubule-binding protein Bim1p form a large patch across the exterior-facing surface of alpha-tubulin in the model. Finally, the positions of the mutations suggest that proximity to the alpha-beta interface may account for the finding of synthetic lethality of five viable tub1 alleles with the benomyl-resistant but otherwise entirely viable tub2-201 allele.
Richards
K L
KL
Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA.
Anders
K R
KR
Nogales
E
E
Schwartz
K
K
Downing
K H
KH
Botstein
D
D
D000818:Animals; D001542:Benomyl / Q000378:metabolism; D001665:Binding Sites; D002417:Cattle; D018797:Cell Cycle Proteins / Q000378:metabolism; D003080:Cold Temperature; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008868:Microtubule Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D008958:Models, Molecular; D005810:Multigene Family; D009154:Mutation; D010641:Phenotype; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D013329:Structure-Activity Relationship; D014404:Tubulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
C119683:BIM1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D008868:Microtubule Proteins; D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin; D001542:Benomyl