title: Diversification of Paralogous α-Isopropylmalate Synthases by Modulation of Feedback Control and Hetero-Oligomerization in Saccharomyces cerevisiae.
abstract: Production of α-isopropylmalate (α-IPM) is critical for leucine biosynthesis and for the global control of metabolism. The budding yeast Saccharomyces cerevisiae has two paralogous genes, LEU4 and LEU9, that encode α-IPM synthase (α-IPMS) isozymes. Little is known about the biochemical differences between these two α-IPMS isoenzymes. Here, we show that the Leu4 homodimer is a leucine-sensitive isoform, while the Leu9 homodimer is resistant to such feedback inhibition. The leu4Δ mutant, which expresses only the feedback-resistant Leu9 homodimer, grows slowly with either glucose or ethanol and accumulates elevated pools of leucine; this phenotype is alleviated by the addition of leucine. Transformation of the leu4Δ mutant with a centromeric plasmid carrying LEU4 restored the wild-type phenotype. Bimolecular fluorescent complementation analysis showed that Leu4-Leu9 heterodimeric isozymes are formed in vivo. Purification and kinetic analysis showed that the hetero-oligomeric isozyme has a distinct leucine sensitivity behavior. Determination of α-IPMS activity in ethanol-grown cultures showed that α-IPM biosynthesis and growth under these respiratory conditions depend on the feedback-sensitive Leu4 homodimer. We conclude that retention and further diversification of two yeast α-IPMSs have resulted in a specific regulatory system that controls the leucine-α-IPM biosynthetic pathway by selective feedback sensitivity of homomeric and heterodimeric isoforms.
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico glopez@email.ifc.unam.mx.
authors.forename: Geovani
authors.initials: G
authors.lastname: López
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Héctor
authors.initials: H
authors.lastname: Quezada
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Mariana
authors.initials: M
authors.lastname: Duhne
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: James
authors.initials: J
authors.lastname: González
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Mijail
authors.initials: M
authors.lastname: Lezama
authors.affiliation: Departamento de Biomedicina Cardiovascular, Instituto Nacional Cardiología Ignacio Chávez, Juan Badiano No. 1, Colonia Sección XVI, Tlalpan, Mexico City, Mexico.
authors.forename: Mohammed
authors.initials: M
authors.lastname: El-Hafidi
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Maritrini
authors.initials: M
authors.lastname: Colón
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Ximena
authors.initials: X
authors.lastname: Martínez de la Escalera
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Mirelle Citlali
authors.initials: MC
authors.lastname: Flores-Villegas
authors.affiliation: Deptartment of Microbiology, Imperial College London, South Kensington Campus, London, United Kingdom Institut de Génétique et Microbiologie, CNRS UMR 8621, Université Paris-Sud, Orsay, France.
authors.forename: Claudio
authors.initials: C
authors.lastname: Scazzocchio
authors.affiliation: Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y Estudios Avanzados del IPN, Irapuato, Guanajuato, Mexico.
authors.forename: Alexander
authors.initials: A
authors.lastname: DeLuna
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Alicia
authors.initials: A
authors.lastname: González
mesh_terms: D015079:2-Isopropylmalate Synthase / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C000605328:LEU9 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015079:2-Isopropylmalate Synthase; C080062:LEU4 protein, S cerevisiae
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