The Crystal Structure of Indole-3-glycerol Phosphate Synthase from the Hyperthermophilic ArchaeonSulfolobus solfataricusin Three Different Crystal Forms: Effects of Ionic Strength

Knöchel, Thorsten; Hennig, Michael; Merz, Astrid; Darimont, Beatrice; Kirschner, Kasper; Jansonius, Johan N.

doi:10.1006/jmbi.1996.0531

Cited by 35 publications

(38 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Crystallization and Intermolecular Disulfide FormationtIGPS was crystallized with polyethylene glycol 8000 as precipitant, in buffer conditions that were similar to those resulting in crystal form B of sIGPS (20). The crystals of tIGPS belong to space group P4 3 with cell dimensions a ϭ b ϭ 48.9 Å, c ϭ 248.0 Å and ␣ ϭ ␤ ϭ ␥ ϭ 90°.…”

Section: Resultsmentioning

confidence: 99%

“…The best crystals were grown by hanging drop vapor diffusion at 4°C by mixing 2 or 4 l of protein solution with 2 l of a reservoir solution containing 8 -11% (w/v) polyethylene glycol 8000 and 160 -180 mM ammonium sulfate, buffered with 100 mM sodium cacodylate at pH 6.0. These conditions are similar to those used for growing crystals of form B of sIGPS (20).…”

Section: Methodsmentioning

confidence: 99%

“…In both molecules, 92% of the residues are in the most favored regions of the Ramachandran diagram (28), whereas 7.6% are in additionally allowed areas. An exception is Ser ) have similar disallowed , angles (14,19,20).…”

Section: Methodsmentioning

confidence: 99%

“…1c) illustrates that tIGPS shares the (␤␣) 8 -barrel fold with both eIGPS (14,34) and sIGPS (19,20), including the N-terminal extension of 44 residues and the extra helix ␣ 8 Ј that is located in the loop between strand ␤ 8 and helix ␣ 8 . A unique structural feature of tIGPS is helix ␣ 7 , which is completely in the 3 10 -helical conformation, in contrast to ␣ 7 of eIGPS and sIGPS, where regular ␣-helices are formed.…”

Section: Thermostability Of Igps From T Maritimamentioning

confidence: 99%

“…In contrast to tPRAI, the thermostable IGPS from Sulfolobus solfataricus (sIGPS) is monomeric, and structural comparisons (19,20) suggested that sIGPS is stabilized mainly by having almost twice as many salt bridges as eIGPS. In the same vein, the ␣-subunit of tryptophan synthase from Pyrococcus furiosus, another monomeric, thermostable (␤␣) 8 -barrel protein involved in tryptophan biosynthesis, possesses almost three times as many ion pairs as its orthologue from E. coli (21).…”

mentioning

confidence: 99%

See 4 more Smart Citations

The Crystal Structure of Indoleglycerol-phosphate Synthase from Thermotoga maritima

Knöchel¹,

Pappenberger²,

Jansonius³

et al. 2002

Journal of Biological Chemistry

View full text Add to dashboard Cite

The crystal structure of the thermostable indoleglycerol-phosphate synthase from Thermotoga maritima (tIGPS) was determined at 2.5 Å resolution. It was compared with the structures of the thermostable sIGPS from Sulfolobus solfataricus and of the thermolabile eIGPS from Escherichia coli. The main chains of the three (␤␣) 8 ؊barrel proteins superimpose closely, and the packing of side chains in the ␤-barrel cores, as well as the architecture of surface loops, is very similar. Both thermostable proteins have, however, 17 strong salt bridges, compared with only 10 in eIGPS. The number of additional salt bridges in tIGPS and sIGPS correlates well with their reduced rate of irreversible thermal inactivation at 90°C. Only 3 of 17 salt bridges in tIGPS and sIGPS are topologically conserved. The major difference between the two proteins is the preference for interhelical salt bridges in sIGPS and intrahelical ones in tIGPS. The different implementation of salt bridges in the closely related proteins suggests that the stabilizing effect of salt bridges depends rather on the sum of their individual contributions than on their location. This observation is consistent with a protein unfolding mechanism where the simultaneous breakdown of all salt bridges is the rate-determining step.It is important to understand how thermophilic organisms stabilize their proteins (1-3). Further insights into the structural features essential for protein stability will improve our understanding of how protein thermostability may have been lost or gained during evolution, and how proteins from mesophilic organisms might be stabilized for industrial applications (4).Comprehensive comparisons of structural features of protein families from mesophiles and thermophiles (5, 6) have confirmed earlier observations that the majority of thermostable proteins has an increased number of salt bridges, as compared with their thermolabile counterparts. The picture of salt bridges generally strengthening thermostable proteins has, however, been modified by recent work. Computational studies (7), as well as tests of specific stabilizing interactions in small proteins conducted by replacing specific residues (8 -11), have shown that the decisive feature is rather the optimal placement of charged residues on the protein surface.We are interested in how the (␤␣) 8 Ϫbarrel fold (12), which is frequently observed in enzymes with quite different functions (13), is stabilized in thermophilic organisms. We have previously studied the (␤␣) 8 -barrel enzymes phosphoribosyl-anthranilate isomerase (PRAI) 1 and indoleglycerol-phosphate synthase (IGPS), which catalyze two consecutive steps in the pathway of tryptophan biosynthesis. In Escherichia coli (14), IGPS and PRAI are the covalently linked domains of the bifunctional enzyme eIGPS-ePRAI. The genetically separated ePRAI and eIGPS domains are fully active monomers (15), but their covalent linkage in the parental protein is advantageous, because it stabilizes the particularly labile eIGPS domain.Previous comparisons of...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%