Structural basis for L-lysine feedback inhibition of homocitrate synthase.
J Biol Chem
; 285(14): 10446-53, 2010 Apr 02.
Article
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| MEDLINE
| ID: mdl-20089861
ABSTRACT
The alpha-aminoadipate pathway of lysine biosynthesis is modulated at the transcriptional and biochemical levels by feedback inhibition. The first enzyme in the alpha-aminoadipate pathway, homocitrate synthase (HCS), is the target of the feedback regulation and is strongly inhibited by l-lysine. Here we report the structure of Schizosaccharomyces pombe HCS (SpHCS) in complex with l-lysine. The structure illustrates that the amino acid directly competes with the substrate 2-oxoglutarate for binding within the active site of HCS. Differential recognition of the substrate and inhibitor is achieved via a switch position within the (alpha/beta)(8) TIM barrel of the enzyme that can distinguish between the C5-carboxylate group of 2-oxoglutarate and the epsilon-ammonium group of l-lysine. In vitro and in vivo assays demonstrate that mutations of the switch residues, which interact with the l-lysine epsilon-ammonium group, abrogate feedback inhibition, as do substitutions of residues within the C-terminal domain that were identified in a previous study of l-lysine-insensitive HCS mutants in Saccharomyces cerevisiae. Together, these results yield new insights into the mechanism of feedback regulation of an enzyme central to lysine biosynthesis.
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Bases de datos:
MEDLINE
Asunto principal:
Schizosaccharomyces
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Retroalimentación Fisiológica
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Oxo-Ácido-Liasas
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Lisina
Idioma:
En
Revista:
J Biol Chem
Año:
2010
Tipo del documento:
Article
País de afiliación:
Estados Unidos