Paramyxovirus matrix protein is believed to play a crucial role in the assembly and maturation of the virus particle by bringing the major viral components together at the budding site in the host cell. The membrane association capability of many enveloped virus matrix proteins has been characterized to be their intrinsic property. In this work, we have characterized the membrane association of Rinderpest virus matrix (M) protein. The M protein of Rinderpest virus when expressed in the absence of other viral proteins is present both in the cytoplasm and plasma membrane. When expressed as GFP fusion protein, the M protein gets localized into plasma membrane protrusions. High salt and alkaline conditions resulted in partial dissociation of M protein from cell membrane. Thus, M protein behaves like an integral membrane protein although its primary structure suggests it to be a peripheral membrane protein. (c) 2007 Elsevier Inc. All rights reserved.