Crystal structures and enzymatic properties of three formyltransferases from archaea: environmental adaptation and evolutionary relationship.
Formyltransferase catalyzes the reversible formation of formylmethanofuran from N(5)-formyltetrahydromethanopterin and methanofuran, a reaction involved in the C1 metabolism of methanogenic and sulfate-reducing archaea. The crystal structure of the homotetrameric enzyme from Methanopyrus kandleri (growth temperature optimum 98 degrees C) has recently been solved at 1.65 A resolution. We report here the crystal structures of the formyltransferase from Methanosarcina barkeri (growth temperature optimum 37 degrees C) and from Archaeoglobus fulgidus (growth temperature optimum 83 degrees C) at 1.9 A and 2.0 A resolution, respectively. Comparison of the structures of the three enzymes revealed very similar folds. The most striking difference found was the negative surface charge, which was -32 for the M. kandleri enzyme, only -8 for the M. barkeri enzyme, and -11 for the A. fulgidus enzyme. The hydrophobic surface fraction was 50% for the M. kandleri enzyme, 56% for the M. barkeri enzyme, and 57% for the A. fulgidus enzyme. These differences most likely reflect the adaptation of the enzyme to different cytoplasmic concentrations of potassium cyclic 2,3-diphosphoglycerate, which are very high in M. kandleri (>1 M) and relatively low in M. barkeri and A. fulgidus. Formyltransferase is in a monomer/dimer/tetramer equilibrium that is dependent on the salt concentration. Only the dimers and tetramers are active, and only the tetramers are thermostable. The enzyme from M. kandleri is a tetramer, which is active and thermostable only at high concentrations of potassium phosphate (>1 M) or potassium cyclic 2,3-diphosphoglycerate. Conversely, the enzyme from M. barkeri and A. fulgidus already showed these properties, activity and stability, at much lower concentrations of these strong salting-out salts.
Mamat
Björn
B
Max-Planck-Institut für Biophysik, D-60528 Frankfurt am Main, Germany Institut für Biophysik der Johann Wolfgang Goethe-Universität, D-60590 Frankfurt am Main, Germany.
Roth
Annette
A
Grimm
Clemens
C
Ermler
Ulrich
U
Tziatzios
Christos
C
Schubert
Dieter
D
Thauer
Rudolf K
RK
Shima
Seigo
S
D019611:Archaeoglobus fulgidus / Q000201:enzymology*; D018360:Crystallography, X-Ray; D004777:Environment; D019605:Euryarchaeota / Q000201:enzymology*; D019143:Evolution, Molecular; D019877:Hydroxymethyl and Formyl Transferases / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017021:Methanosarcina barkeri / Q000201:enzymology*; D008958:Models, Molecular; D010802:Phylogeny; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D013696:Temperature; D014461:Ultracentrifugation
D021122:Protein Subunits; D019877:Hydroxymethyl and Formyl Transferases