1ibt
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STRUCTURE OF THE D53,54N MUTANT OF HISTIDINE DECARBOXYLASE AT-170 C
OverviewOverview
Histidine decarboxylase (HDC) from Lactobacillus 30a converts histidine to, histamine, a process that enables the bacteria to maintain the optimum pH, range for cell growth. HDC is regulated by pH; it is active at low pH and, inactive at neutral to alkaline pH. The X-ray structure of HDC at pH 8, revealed that a helix was disordered, resulting in the disruption of the, substrate-binding site. The HDC trimer has also been shown to exhibit, cooperative kinetics at neutral pH, that is, histidine can trigger a, T-state to R-state transition. The D53,54N mutant of HDC has an elevated, Km, even at low pH, indicating that the enzyme assumes the low activity, T-state. We have solved the structures of the D53,54N mutant at low pH, with and without the substrate analog histidine methyl ester (HME) bound., Structural analysis shows that the apo-D53,54N mutant is in the inactive, or T-state and that binding of the substrate analog induces the enzyme to, adopt the active or R-state. A mechanism for the cooperative transition is, proposed.
About this StructureAbout this Structure
1IBT is a Protein complex structure of sequences from Lactobacillus sp.. Active as Histidine decarboxylase, with EC number 4.1.1.22 Full crystallographic information is available from OCA.
ReferenceReference
Structure and cooperativity of a T-state mutant of histidine decarboxylase from Lactobacillus 30a., Worley S, Schelp E, Monzingo AF, Ernst S, Robertus JD, Proteins. 2002 Feb 15;46(3):321-9. PMID:11835507
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