Ubiquitin complex proteins

FIGURE 4.49 Isolation of a complex protein conjugate on Toyopearl HW-50S. Column 22 mm X 83 cm. Sample Fraction from crude Tetrahymena H2A containing the ubiquitin-histone conjugate uH2A. Elution 10 nM HCI. Flow rate 0.1 ml/min. Detection UV at 230 nm. 

J. M., Jiang, W., Liu, Y., Callis, J., Goebl, M., and Estelle, M. Modification of yeast Cdc53p by the ubiquitin-related protein rub Ip affects function of the SCFCdc4 complex. Genes Dev 1998, 12, 914-926. 

The structure of the APPBP1-UBA3-NEDD8-ATP complex reveals the basis for selective ubiquitin-like protein activation by an El, Mol Cell 2003, 32, 1427-1437. 

Mahajan, R., Delphin, C., Guan, T., Geeace, L., and Melchior, F. A small ubiquitin-related polypeptide involved in targeting RanGAPl to nuclear pore complex protein RanBP2, Cell, 1997, 88, 97-107. 

Rasmussen, T. P., Culbertson, M. R., and Hochsteasser, M. The yeast SEN3 gene encodes a regulatory subunit of the 26 S proteasome complex required for ubiquitin-dependent protein degradation in vivo. Mol. Cell. Biol. 1995, 35, 6311-6321. 

The three-dimensional structure of both UBA domains of the human Rad23a proteins have been solved and reveal a conserved three-helix bundle fold [50, 51], So far, no structure of a UBA-ubiquitin complex is known and we can only speculate on their mode of interaction. The original UBA structures revealed two... 

Luders, j., Pyrowolakis, G., and Jentsch, S., The ubiquitin-like protein HUBl forms SDS-resistant complexes with cellular proteins in the absence of ATP, EMBO Rep., 2003, 4, 1169. 

In addition to the intrinsic subunits, proteins that interact with the proteasome complex regulate its activity/ Often the cofactors are components of the ubiquitin pathway. Proteins such as chaperones and heat-shock proteins also assist in proteasome-mediated degradation of proteins. 

Multiubiquitination of intracellular proteins is a prerequisite for the selective degradation of intracellular proteins by the ubiquitin-dependent proteolytic pathway [236,237]. Monoubiquitinated histones are not degraded by the protea-some [238,239]. Proteasome, a multisubunit complex that catalyzes both ubiquitin-dependent and ubiquitin-independent protein degradation, is found in the cytoplasm and nucleus [240-242]. Thus, it is possible that multiubiquitination of the histones may tag these proteins for degradation. 

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