x-ray-crystallography-to-study-oligomeric-state-transition-thermotoga

X-Ray Crystallography to Study the Oligomeric State Transition of the <em>Thermotoga maritima</em> M42 Aminopeptidase TmPep1050

The M42 aminopeptidases form functionally active complexes made of 12 subunits. Their assembly process appears to be regulated by their metal ion ...

Université Libre de Bruxelles

Labiris Institut de Recherche

The peptide F2L was previously characterized as a high-affinity natural agonist for the human formyl peptide receptor (FPR) 3. F2L is an acetylated 21-aa peptide corresponding with the N terminus of the intracellular heme-binding protein 1 (HEBP1). In the current work, we have investigated which proteases were able to generate the F2L peptide from its precursor HEBP1. Structure-function analysis of F2L identified three amino acids, G(3), N(7), and S(8), as the most important for interaction of the peptide with FPR3. We expressed a C-terminally His-tagged form of human HEBP1 in yeast and purified it to homogeneity. The purified protein was used as substrate to identify proteases generating bioactive peptides for FPR3-expressing cells. A conditioned medium from human monocyte-derived macrophages was able to generate bioactivity from HEBP1, and this activity was inhibited by pepstatin A. Cathepsin D was characterized as the protease responsible for HEBP1 processing, and the bioactive product was identified as F2L. We have therefore determined how F2L, the specific agonist of FPR3, is generated from the intracellular protein HEBP1, although it is unknown in which compartment the processing by cathepsin D occurs in vivo.

Processing of HEBP1 by cathepsin D gives rise to F2L, the agonist of formyl peptide receptor 3.

The discovery of new glycoside hydrolases that can be utilized in the chemoenzymatic synthesis of carbohydrates has emerged as a promising approach for various biotechnological processes. In this study, recombinant Ps_Cel5A from Pseudomonas stutzeri A1501, a novel member of the GH5_5 subfamily, was expressed, purified and crystallized. Preliminary experiments confirmed the ability of Ps_Cel5A to catalyze transglycosylation with cellotriose as a substrate. The crystal structure revealed several structural determinants in and around the positive subsites, providing a molecular basis for a better understanding of the mechanisms that promote and favour synthesis rather than hydrolysis. In the positive subsites, two nonconserved positively charged residues (Arg178 and Lys216) were found to interact with cellobiose. This adaptation has also been reported for transglycosylating β-mannanases of the GH5_7 subfamily.

Crystal structure determination of Pseudomonas stutzeri A1501 endoglucanase Cel5A: the search for a molecular basis for glycosynthesis in GH5_5 enzymes.

The M42 aminopeptidases are dinuclear aminopeptidases displaying a peculiar tetrahedron-shaped structure with 12 subunits. Their quaternary structure results from the self-assembly of six dimers controlled by their divalent metal ion cofactors. The oligomeric-state transition remains debated despite the structural characterization of several archaeal M42 aminopeptidases. The main bottleneck is the lack of dimer structures, hindering the understanding of structural changes occurring during the oligomerization process. We present the first dimer structure of an M42 aminopeptidase, TmPep1050 of , along with the dodecamer structure. The comparison of both structures has allowed us to describe how the metal ion cofactors modulate the active-site fold and, subsequently, affect the interaction interface between dimers. A mutational study shows that the M1 site strictly controls dodecamer formation. The dodecamer structure of TmPep1050 also reveals that a part of the dimerization domain delimits the catalytic pocket and could participate in substrate binding.

Raphael Dutoit

Laboratory of Microbiology,
Department of Molecular Biology,
Laboratory of Microbiology, Department of Molecular Biology

Université Libre de Bruxelles

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Raphael Dutoit

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Laboratory of Microbiology,Department of Molecular Biology,Laboratory of Microbiology, Department of Molecular Biology

Université Libre de Bruxelles

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Laboratory of Microbiology,
Department of Molecular Biology,
Laboratory of Microbiology, Department of Molecular Biology