Electron spectroscopic imaging of the centrosome in cells of the Indian muntjac.

Specific antibody labelling indicates that phosphoproteins are present at microtubule-organizing centres, including the centrosome. We have employed electron spectroscopic imaging techniques that permit high-resolution elemental analysis of thin sections of intact cells to investigate the precise distribution of phosphorus and therefore phosphoproteins at the centrosome of Indian muntjac cells. We report that these proteins are localized to both the pericentriolar matrix and the centriole. The matrix contains an abundance of phosphorus and is associated with microtubule elements. Within the mature centriole, major structures including the nine triplet blades and linking elements that connect adjacent blades are composed of phosphorylated proteins. In addition, phosphoproteins are abundant at the ends of the centriole, at the interface between the centriole lumen and the pericentriolar environment. From these observations we suggest that phosphoproteins may play both a structural and a functional role within the centrosome region.