ABSTRACT
A monoclonal antibody (mcab) raised against a subcellular fraction of Sarcocystis muris cystozoites was used to localize microneme antigens before, during and after invasion of cultured cells. The mcab recognized a 20 and 22 kDa protein under reducing and non-reducing conditions on Western blots and localized an antigen in cystozoites in the apical part of the parasites. Confocal laser scanning microscopy of invading cystozoites revealed the secretion of a microneme antigen at the apical tip of the parasite. The secreted microneme antigen was attached to the host cell surface at the invasion site and spread along the surface of the infected cells. Electron microscopy using immunogold labeling showed that the microneme antigen was distributed in patches on the surface of infected cells and present on infected cells more than 60 min post-infection. The function of microneme antigens during parasite-host cell interactions is discussed.
Subject(s)
Coccidia/ultrastructure , Organelles/metabolism , Animals , Blotting, Western , Cats , Cells, Cultured , Coccidia/physiology , Electrophoresis, Polyacrylamide Gel , Fluorescent Antibody Technique , Lasers , Mice , Microscopy, ImmunoelectronABSTRACT
On the basis of an elaborate conformational analysis of m1- and m2-selective antagonists a respective pharmacophore was deduced. This then was introduced into models of the two muscarinic receptor subtypes. These models were constructed starting from bacteriorhodopsin as a template in accordance with alignment data and mutation experiments. The validity of the interaction geometries between ligands and receptor subtypes is supported by a significant correlation between calculated interaction energies and experimentally determined affinity data.