Binding to retinoblastoma pocket domain does not alter the inter-domain flexibility of the J domain of SV40 large T antigen.
Simian Virus 40 uses the large T antigen (Tag) to bind and inactivate retinoblastoma tumor suppressor proteins (Rb), which can result in cellular transformation. Tag is a modular protein with four domains connected by flexible linkers. The N-terminal J domain of Tag is necessary for Rb inactivation. Binding of Rb is mediated by an LXCXE consensus motif immediately C-terminal to the J domain. Nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS) were used to study the structural dynamics and interaction of Rb with the LXCXE motif, the J domain and a construct (N(260)) extending from the J domain through the origin binding domain (OBD). NMR and SAXS data revealed substantial flexibility between the domains in N(260). Binding of pRb to a construct containing the LXCXE motif and the J domain revealed weak interactions between pRb and the J domain. Analysis of the complex of pRb and N(260) indicated that the OBD is not involved and retains its dynamic independence from the remainder of Tag. These results support a 'chaperone' model in which the J domain of Tag changes its orientation as it acts upon different protein complexes.
Department of Biochemistry, Vanderbilt University, Nashville, TN 37232-8725, USA.
Christina K
CK
Williams
Sivaraja
S
Vaithiyalingam
Michal
M
Hammel
James
J
Pipas
Walter J
WJ
Chazin
D020816:Amino Acid Motifs; D000952:Antigens, Polyomavirus Transforming / Q000737:chemistry* / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016160:Retinoblastoma Protein / Q000737:chemistry* / Q000378:metabolism
D000952:Antigens, Polyomavirus Transforming; D046912:Multiprotein Complexes; D016160:Retinoblastoma Protein