The Biotinyl Domain of Escherichia coli Acetyl-CoA Carboxylase

Subsequent enzymatic work localized the defect to acetyl-CoA carboxylase; and the results reported were ambiguous, the strain was found to contain decreased levels of Biotin carboxyl carrier protein, the biotinylated form of AccB, when grown at 30 °C

John E. Cronan

2002

Scholarcy highlights

  • Acetyl-CoA carboxylase1 catalyzes the first step in fatty acid synthesis, the synthesis of malonyl-CoA from acetylCoA
  • In virtually all biotinylated proteins, the site of biotin attachment is a lysine side chain found at the center of a strongly conserved sequence of ϳ70 amino acid residues located at the carboxyl termini of the proteins
  • Subsequent enzymatic work localized the defect to acetyl-CoA carboxylase; and the results reported were ambiguous, the strain was found to contain decreased levels of Biotin carboxyl carrier protein, the biotinylated form of AccB, when grown at 30 °C
  • The recent structures of the AccB biotinoyl domain showed that Gly133 is a key residue in the turn linking ␤-sheets 5 and 6, and modeling showed that steric clashes result upon substitution with larger residues
  • Upon alignment, the biotinoyl domains clearly fall into two classes, those that have the thumb insertion found in E. coli BCCP and those lacking this sequence
  • Among the biotin-dependent enzymes of known specificity, all of the acetyl-CoA carboxylase biotinoyl domains have the thumb sequence, whereas the thumb-less domains are from enzymes that catalyze reactions other than malonyl-CoA synthesis
  • Complementation by Unbiotinylated Biotin carboxyl carrier protein—The observed complementation of the temperature-sensitive G133S mutation by expression of mutant AccB proteins that cannot be biotinylated demonstrates an unanticipated complexity of the acetyl-CoA carboxylase reaction

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