Structure of HisF, a histidine biosynthetic protein fromPyrobaculum aerophilum

Abstract

HisF (imidazole glycerol phosphate synthase) is an important branch-point enzyme in the histidine biosynthetic pathway of microorganisms. Because of its potential relevance for structure-based drug design, the crystal structure of HisF from the hyperthermophilic archaeon Pyrobaculum aerophilum has been determined. The structure was determined by molecular replacement and refined at 2.0 A resolution to a crystallographic R factor of 20.6% and a free R of 22.7%. The structure adopts a classic (beta/alpha)(8) barrel fold and has networks of surface salt bridges that may contribute to thermostability. The active site is marked out by the presence of two bound phosphate ions and two glycerol molecules that delineate a long groove at one end of the (beta/alpha)(8) barrel. The two phosphate ions, 17 A apart, are bound to sequence-conserved structural motifs that seem likely to provide much of the specificity for the two phosphate groups of the HisF substrate. The two glycerol molecules bind in the vicinity of other sequence-conserved residues that are likely to be involved in binding and/or catalysis. Comparisons with the homologous HisF from Thermatoga maritima reveal a displaced loop that may serve as a lid over the active site.

Two‐fold repeated (βα) 4 half‐barrels may provide a molecular tool for dual substrate specificity

“…Data and refinement statistics are shown in supplementary information online. The initial phases were obtained from molecular replacement using MOLREP (Vagin & Teplyakov, 1997), and using Protein Data Bank (PDB) entry 1H5Y (Banfield et al , 2001) as a search model. The structure was refined by alternating rounds of manual model building in COOT (http://www.ysbl.york.ac.uk/~emsley/coot/) and refinement with REFMAC (Murshudov et al , 1997).…”

Crystal structure of glutamine amidotransferase from Thermotoga maritima

“…Here, we present the crystal structure of the HisH protein from Thermotoga maritima (TmHisH), which complements the known structure of HisF from the same organism (TmHisF)5 [Protein Data Bank (PDB) ID 1THF] and HisF from Pyrobaculum aerophilum 6 (PDB ID 1H5Y) and shows high structural similarity with the glutaminase domain of the recently determined structure of IGSP from yeast7 (HIS7) (PDB ID 1JVN).…”

Structural Studies of the Catalytic Reaction Pathway of a Hyperthermophilic Histidinol-phosphate Aminotransferase

“…Thermal Stabilization-Structures of several enzymes of the histidine biosynthesis pathway from the hyperthermophile T. maritima have already been determined, including tmHisA (23), tmHisF (23), tmHisH (24), the binary tmHisH-tmHisF complex (24), and the hetero-octameric tmHisG-tmHisZ complex, 2 thereby allowing comparisons with the respective enzyme structures from mesophilic organisms (25)(26)(27)(28). Previous statistical analyses of large structural data sets revealed that the frequency of salt bridges, surface polarity, and structural compactness may be important criteria that affect the structural parameters for thermal stabilization, in general (29,30), and in T. maritima, in particular (31,32).…”