STUB1 (STIP1 homology and U-box-containing protein 1, also known as C-terminus of Hsc70-interacting protein, CHIP) is a 35 kDa ubiquitin ligase that participates in intracellular protein folding/refolding and degradation. STUB1 is highly expressed in striated muscle. STUB1 may complex with the molecular chaperones Hsp70 and Hsp90, or act by itself, to regulate protein stability and ubiquitination.
Human STUB1 is 303 amino acids (aa) in length. It contains one TPR domain (aa 27 - 127) plus a C-terminal U-Box (aa 226 - 299). Its TRP domain interacts with heat shock proteins, while the U-Box participates in ubiquitination. There is one STUB1 isoform that shows an alternate start site at Met73. Human and mouse STUB1 are 97% aa identical.