6 research outputs found
Membrane orientation of laminin binding protein An extracellular matrix bridging molecule of Leishmania donovani
Earlier we presented several lines of evidence that a 67-kDa
laminin binding protein (LBP) in Leishmania donovani, that
is di.erent from the putative mammalian 67-kDa laminin
receptor, may play an important role in the onset of leishmaniasis,
as these parasites invade macrophages in various
organs after migrating through the extracellular matrix.
Here we describe the membrane orientation of this Leishmania
laminin receptor. Flow cytometric analysis using anti-
LBP Ig revealed its surface localization, which was further
con.rmed by enzymatic radiolabeling of Leishmania surface
proteins, autoradiography and Western blotting. E.cient
incorporation of LBP into arti.cial lipid bilayer, as well as its
presence in the detergent phase after Triton X-114 membrane
extraction, suggests that it may be an integral membrane
protein. Limited trypsinization of intact parasite and
subsequent immunoblotting of trypsin released material
using laminin as primary probe revealed that amajor part of
this protein harbouring the laminin binding site is oriented
extracellularly. Carboxypeptidase Y treatment of the whole
cell, as well as the membrane preparation, revealed that a
small part of the C-terminal is located in the cytosol. A
34-kDa transmembrane part of LBP could be identi.ed
using the photoactive probe, 3-(tri.uoromethyl)-3-(m-iodophenyl)
diazirine (TID). Partial sequence comparison of the
intact protein to that with the trypsin-released fragment
indicated that N-terminal may be located extracellularly.
Together, these results suggest that LBP may be an integral
membrane protein, having signi.cant portion of N-terminal
end as well as the laminin binding site oriented extracellularly,
a membrane spanning domain and a C-terminal
cytosolic end