Membrane orientation of laminin binding protein

Area of Science:

• Parasitology
• Molecular Biology
• Cell Biology

Background:

• Leishmania donovani parasites invade macrophages, a process potentially mediated by surface proteins.
• A 67-kDa laminin binding protein (LBP) in Leishmania has been implicated in leishmaniasis onset.
• The membrane orientation of this Leishmania LBP was previously unknown.

Purpose of the Study:

• To determine the membrane orientation of the Leishmania donovani 67-kDa laminin binding protein (LBP).
• To elucidate the structural domains of LBP involved in parasite-host interactions.

Main Methods:

• Flow cytometry and enzymatic radiolabeling to confirm surface localization.
• Triton X-114 extraction and lipid bilayer incorporation to assess membrane integration.
• Limited trypsinization and carboxypeptidase Y treatment to identify exposed protein domains.
• Photoaffinity labeling with TID to identify the transmembrane region.

Main Results:

• LBP is localized on the Leishmania surface and is an integral membrane protein.
• The laminin binding site and a significant portion of the N-terminus are extracellular.
• A 34-kDa transmembrane domain was identified.
• A small C-terminal portion is located in the cytosol.

Conclusions:

• Leishmania donovani LBP is an integral membrane protein with a complex topology.
• Its extracellular domains facilitate laminin binding and parasite invasion.
• The transmembrane and cytosolic domains likely play roles in anchoring and signaling.