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The crystal structure of the Leishmania major surface proteinase leishmanolysin (gp63)
E Schlagenhauf1, R Etges, P Metcalf
1EMBL Heidelberg, Biological Structures and Biocomputing Programme, Germany.
Background:
Despite their medical importance, there is little available structural information for the surface antigens of infectious protozoa. Diseases caused by the protozoan parasite Leishmania are common in many developing countries. Human infection occurs during the bite of infected sandfilies, when Leishmania promastigote cells from the insect gut enter the bloodstream. Promastigotes in the blood parasitize macrophages, often causing serious disease. Leishmanolysin is the predominant protein surface antigen of promastigotes, and is assumed to have a key role during infection. Leishmanolysin is a membrane-bound zinc proteinase, active in situ. Similar molecules exist in other trypanomastid protozoa.
Results:
Two crystal forms of leishmanolysin were obtained from protein purified from promastigote membranes. A single lead derivative in both crystal forms was used to solve the structure. The structure reveals three domains, two of which have novel folds. The N-terminal domain has a similar structure to the catalytic modules of zinc proteinases. The structure clearly shows that leishmanolysin is a member of the metzincin class of zinc proteinases.
Conclusions:
The unexpected metzincin features of the leishmanolysin structure suggest that the metzincin fold may be more widespread than indicated by sequence homologies amongst existing metzincin zinc proteinases. The similarity of the active-site structure to previously well characterized metzincin class zinc proteinases should aid the development of specific inhibitors. These inhibitors might be used to determine the function of leishmanolysin in the insect and during mammalian infection, and may aid the development of drugs for human leishmaniasis.
Insights
Structural analysis of leishmanolysin, a key surface antigen of Leishmania parasites, reveals it belongs to the metzincin class of zinc proteinases, aiding potential drug development for leishmaniasis.
Area of Science:
- Structural biology
- Parasitology
- Biochemistry
Background:
- Leishmania surface antigens lack structural information, hindering understanding of protozoan infections.
- Leishmanolysin is a crucial surface protein of Leishmania promastigotes, involved in host infection.
- Leishmanolysin is a membrane-bound, active zinc proteinase found in other trypanomastid protozoa.
Purpose of the Study:
- To determine the three-dimensional structure of leishmanolysin.
- To classify leishmanolysin within known protein families.
- To identify potential targets for therapeutic intervention against leishmaniasis.
Main Methods:
- Protein purification from Leishmania promastigote membranes.
- Crystallization of leishmanolysin in two different forms.
- X-ray crystallography and heavy atom derivative phasing to solve the protein structure.
Main Results:
- Two crystal forms of leishmanolysin were successfully obtained and analyzed.
- The leishmanolysin structure comprises three domains, with two exhibiting novel folds.
- The N-terminal domain resembles catalytic modules of zinc proteinases, classifying it as a metzincin.
Conclusions:
- The leishmanolysin structure expands the known structural diversity of metzincins beyond sequence homology.
- The active site's similarity to other metzincins facilitates the design of specific inhibitors.
- Inhibitors could elucidate leishmanolysin's function and lead to new drugs for human leishmaniasis.