Novel mechanism for carbamoyl-phosphate synthetase: a nucleotide switch for functionally equivalent domains.
Carbamoyl-phosphate synthetases (CPSs) utilize two molecules of ATP at two internally duplicated domains, B and C. Domains B and C have recently been shown to be structurally [Thoden, J. B., Holden, H. M., Wesenberg, G., Raushel, F. M. & Rayment, I. (1997) Biochemistry 36, 6305-6316] and functionally [Guy, H. I. & Evans, D. R. (1996) J. Biol. Chem. 271, 13762-13769] equivalent. We have carried out a site-directed mutagenic analysis that is consistent with ATP binding to a palmate motif rather than to a Walker A/B motif in domains B and C. To accommodate our present findings, as well as the other recent findings of structural and functional equivalence, we are proposing a novel mechanism for CPS. In this mechanism utilization of ATP bound to domain C is coupled to carbamoyl-phosphate synthesis at domain B via a nucleotide switch, with the energy of ATP hydrolysis at domain C allowing domain B to cycle between two alternative conformations.
Kothe
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M
Department of Biology, Northeastern University, Boston, MA 02115, USA.
Eroglu
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Mazza
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Samudera
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Powers-Lee
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D000595:Amino Acid Sequence; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
D002222:Carbamoyl-Phosphate Synthase (Ammonia); D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)