1IBU

STRUCTURE OF THE D53,54N MUTANT OF HISTIDINE DECARBOXYLASE AT 25 C

Summary for 1IBU

• Entry DOI: 10.2210/pdb1ibu/pdb
• Related: 1HQ6 1IBT 1IBV 1IBW 1PYA
• Descriptor: HISTIDINE DECARBOXYLASE BETA CHAIN, HISTIDINE DECARBOXYLASE ALPHA CHAIN (2 entities in total)
• Functional Keywords: helix disorder, less active form, site-directed mutant, pyruvoyl, carboxy-lyase, lyase
• Biological source: Lactobacillus sp.; More
• Total number of polymer chains: 6
• Total formula weight: 102402.71

Authors

Worley, S.,Schelp, E.,Monzingo, A.F.,Ernst, S.,Robertus, J.D. (deposition date: 2001-03-29, release date: 2002-03-13, Last modification date: 2024-11-06)

Primary citation

Worley, S.,Schelp, E.,Monzingo, A.F.,Ernst, S.,Robertus, J.D.
Structure and cooperativity of a T-state mutant of histidine decarboxylase from Lactobacillus 30a.
Proteins, 46:321-329, 2002

PubMed Abstract: 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.

PubMed: 11835507
DOI: 10.1002/prot.10042

Experimental method

X-RAY DIFFRACTION (3.1 Å)