Abstract
Fractions of 26S and 20S proteasomes isolated from the rabbit brain by the method of salt fractionation (salt-induced precipitation) contain intrinsic proteasome proteins responsible for assembly of the core particle and regulatory particle of proteasome and also proteasome-binding proteins. These proteasome-binding proteins include components of the ubiquitin-proteasome system, some ubiquitinated proteins, as well as cytoskeleton components, protective proteins, regulators of gene expression, cell division, and differentiation, and multifunctional proteins (mainly, glycolytic enzymes: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), aldolase, pyruvate kinase, etc.). The multifunctional proteins also known as "moonlighting proteins" are involved in various (regulatory) processes in the cell and obviously represent important components of the proteasome interactome rather than contaminants of the 26S and 20S proteasome fractions.