Volume 5, Issue 11, Pages 1475-1483 (November 1997) Closed structure of phosphoglycerate kinase from Thermotoga maritima reveals the catalytic mechanism and determinants of thermal stability  Günter Auerbach, Robert Huber, Mira Grättinger, Katrin Zaiss, Hartmut Schurig, Rainer Jaenicke, Uwe Jacob  Structure  Volume 5, Issue 11, Pages 1475-1483 (November 1997) DOI: 10.1016/S0969-2126(97)00297-9

Figure 1 Stereo ribbon diagram of TmPGK with the bound substrates 3-phosphoglycerate (PG) and Mg2+·AMP-PNP (ATP/Mg). Secondary structure elements are marked (helices: h, yellow; strands: s, magenta) and residues either involved in the inter-domain salt bridge (Arg62, Asp200) or catalysis (Arg36, Lys197) are shown in ball-and-stick representation with atoms in standard colours. Structure 1997 5, 1475-1483DOI: (10.1016/S0969-2126(97)00297-9)

Figure 2 Stereo view of the active site of TmPGK showing a central bound water molecule (red sphere) at the putative phosphoryl transition state position. Lys197 is well-orientated for leading the phosphoryl group from the donor BPG to the acceptor ADP during catalysis. A Mg2+ ion (green sphere) is coordinated by three non-bridging oxygen atoms of the triphosphate (α-, β-phosphate in white and γ-phosphate in light green), which differs from the true substrate only in the presence of an imido-  rather than an oxylink between the β-and γ-phosphate of the bound nucleotide. Structure 1997 5, 1475-1483DOI: (10.1016/S0969-2126(97)00297-9)

Figure 3 Stereo view of the superposition of the closed structure of TmPGK (black) with the open structure of BsPGK (red). The central water of the TmPGK structure is shown in blue. A large motion of residue Thr374 (Thr371; BsPGK) towards Arg36 causes a subsequent reorientation of the C-terminal residues Gly375–Gly377 (not labelled). The closed conformation is locked by an inter-domain salt bridge between Arg62 and Asp200 (green). The difference between the inter-domain angles in TmPGK and BsPGK, αTM and αBS, respectively, is 21°. Structure 1997 5, 1475-1483DOI: (10.1016/S0969-2126(97)00297-9)

Figure 4 Structure-based sequence alignment of PGKs from T. maritima, B. stearothermophilus, pig and yeast. Conserved amino acids are marked with blue-shaded boxes. The sequence numbering refers to TmPGK. Secondary structure elements are indicated where s is strand and h is helix. (Figure was made using ALSCRIPT [49].) Structure 1997 5, 1475-1483DOI: (10.1016/S0969-2126(97)00297-9)

Figure 5 Comparison of the structures of the PGKs from T. maritima, B. stearothermophilus, yeast and pig exhibit a drastically reduced interdomain angle between the N-terminal domain (left) and the C-terminal domain (right). The extremely thermostable enzyme from Tm shows a larger number of well-paired surface charges (blue represents positive charges and red represents negative charges) compared to the mesophilic counterparts (Figure was made with GRASP [50]). The yellow frame indicates a possible binding site on TmPGK for triosephosphate isomerase (TmTIM), probably involved in the association of the in vivo tetrameric PGK-TIM fusion protein. Structure 1997 5, 1475-1483DOI: (10.1016/S0969-2126(97)00297-9)