Abstract
The paracrystalline outer membraneous layer (HPI layer) of Micrococcus radiodurans has been investigated by negative- and positive-staining electron microscopy and subsequent digital image processing. The subunit structure of the major HPI layer protein complex and the lipid-protein distribution in the plane of the membrane have been determined. The HPI layer was found to be highly asymmetric in a transmembrane direction, with the major protein complex only partly penetrating into a lipid-containing backing layer intimately associated with it.