Structure and expression of a cyanobacterial ilvC gene encoding acetohydroxyacid isomeroreductase.

AUTOR(ES)

Rieble, S

RESUMO

Acetohydroxyacid isomeroreductase (AHAIR) is the shared second enzyme in the biosynthetic pathways leading to isoleucine and valine. AHAIR is encoded by the ilvC gene in bacteria. A 1,544-bp fragment of genomic DNA containing the ilvC gene was cloned from the cyanobacterium Synechocystis sp. strain PCC 6803, and the complete nucleotide sequence was determined. The identity of the gene was established by comparison of the nucleotide and derived peptide sequences with those of other ilvC genes. The highest degree of sequence similarity was found with the ilvC gene from Rhizobium meliloti. The isolated Synechocystis ilvC gene complemented an Escherichia coli ilvC mutant lacking AHAIR activity. The expressed Synechocystis gene encodes a protein that has a molecular mass of 35.7 kDa and that has AHAIR activity in an in vitro assay. Polyclonal antibodies raised against purified Synechocystis AHAIR produced a single band on a Western blot (immunoblot) of a Synechocystis cell extract and detected the protein in an extract of an E. coli ilvC mutant strain that was transformed with a plasmid containing the Synechocystis ilvC gene. The antibody did not react with an extract of an E. coli ilvC mutant strain that was transformed with a control plasmid lacking the Synechocystis ilvC gene or with an extract of an E. coli IlvC+ control strain.

Documentos Relacionados

• Positive control of ilvC expression in Escherichia coli K-12; identification and mapping of regulatory gene ilvY.
• Mutations in the ilvY gene of Escherichia coli K-12 that cause constitutive expression of ilvC.
• The product of the Rhizobium meliloti ilvC gene is required for isoleucine and valine synthesis and nodulation of alfalfa.
• The ilvB locus of Escherichia coli K-12 is an operon encoding both subunits of acetohydroxyacid synthase I.
• Structure and expression of a pea nuclear gene encoding a chlorophyll a/b-binding polypeptide