Crystal structure determination and functional characterization of the metallochaperone SlyD from Thermus thermophilus.
SlyD (sensitive to lysis D; product of the slyD gene) is a prolyl isomerase [peptidyl-prolyl cis/trans isomerase (PPIase)] of the FK506 binding protein (FKBP) type with chaperone properties. X-ray structures derived from three different crystal forms reveal that SlyD from Thermus thermophilus consists of two domains representing two functional units. PPIase activity is located in a typical FKBP domain, whereas chaperone function is associated with the autonomously folded insert-in-flap (IF) domain. The two isolated domains are stable and functional in solution, but the presence of the IF domain increases the PPIase catalytic efficiency of the FKBP domain by 2 orders of magnitude, suggesting that the two domains act synergistically to assist the folding of polypeptide chains. The substrate binding surface of SlyD from T. thermophilus was mapped by NMR chemical shift perturbations to hydrophobic residues of the IF domain, which exhibits significantly reduced thermodynamic stability according to NMR hydrogen/deuterium exchange and fluorescence equilibrium transition experiments. Based on structural homologies, we hypothesize that this is due to the absence of a stabilizing beta-strand, suggesting in turn a mechanism for chaperone activity by 'donor-strand complementation.' Furthermore, we identified a conserved metal (Ni(2+)) binding site at the C-terminal SlyD-specific helical appendix of the FKBP domain, which may play a role in metalloprotein assembly.
Löw
Christian
C
Institut für Physik, Biophysik, Martin-Luther-Universität Halle-Wittenberg, D-06099 Halle (Saale), Germany.
Neumann
Piotr
P
Tidow
Henning
H
Weininger
Ulrich
U
Haupt
Caroline
C
Friedrich-Epler
Beatrice
B
Scholz
Christian
C
Stubbs
Milton T
MT
Balbach
Jochen
J
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D056511:Metallochaperones / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D016963:Thermus thermophilus / Q000737:chemistry*
D001426:Bacterial Proteins; D056511:Metallochaperones; D019696:Peptidylprolyl Isomerase