CRYSTALLIZATION AND STRUCTURAL DETERMINATION OF MACROPHAGE INFECTIVITY POTENTIATOR PROTEIN (MIP) FROM LEGIONELLA PNEUMOPHILIA
A. Riboldi-Tunnicliffe1, M. S. Weiss1, B. Schmidt2, G. Fischer2 and R. Hilgenfeld1
1 Institute of Molecular
Biotechnology, Department of Structural Biology and
Crystallography, Beutenbergstrasse 11, D-07745, Jena, Germany
2 Max-Plank-Research Unit,
Enzymology of Protein Folding, Halle, Germany
Keywords : Peptidyl Prolyl Cis/Trans Isomerase, PPIase, MIP,
Macrophage Infectivity Potentiator protein Macrophage Infectivity Potentiator protein is one of the major virulence factors (Fischer et al 1992) of the organism Legionella pneumophilia, the causative agent of Legionnaires disease.
MIP belongs to the class of protein peptidyl prolyl cis/trans isomerases (PPIases), these proteins catalyse the cis/trans isomerization of peptidyl-prolyl bonds in oligo peptides. PPIases currently consist of three distinct families, the cyclophillins, the FKBPs and the parvulins. MIP is a member of the FKBPs these bind and are inhibited by the macrolides FK506 and rapamycin, both important as suppressors of T-cell activation (Hacker et al 1993).
The amino acid sequence of MIP revealed the existence of two domains (Ludwig et al 1994). The N-terminal domain, residues 1 - 106, shows no similarity to any known protein, except MIP homologues such as found in L.micdadei and C.psittaci. The C-terminal domain residues (107 - 213) shows a high homology (35% identity, 55% similarity) to human FKBP12 (Hacker et al 1993).
The structure has been partilly solved using molecular replacement with human FKBP12 as the search model. This has given the structure of the C-terminal domain. The structure is still being built with approximatly 90 residues still to fit in the electron density. Crystals have also been grown in complex with both FK506 and rapamycin; both diffract beyond 2.8 A in house. Derivative crystals have also been prepared, but scaling to native data sets is proving difficult.