Mapping the Binding Site of P53 on UBC9 by NMR Spectroscopy

Abstract

AbstractHuman UBC9 is a member of the E2 family of proteins. However, instead of conjugating to ubiquitin, it conjugates to a ubiquitin homologue SUMO‐1 (also known as UBL1, GMP1, SMTP3, PICT‐1 and sentrin). The SUMO‐1 conjugation pathway is very similar to that of ubiquitin with regard to the primary sequences of the ubiquitin activating enzymes (E1), the three‐dimensional structures of the ubiquitin conjugating enzymes (E2), and the chemistry of the overall conjugation pathway. The interaction of p53 and UBC9, the E2 of the SUMO‐1 pathway, has been studied by nuclear magnetic resonance spectroscopy. A peptide corresponding to the nuclear localization domain of p53 specifically interacts with UBC9 and this interaction is likely to be important for conjugation of p53 with SUMO‐1. The largest chemical shift changes on UBC9 occur at residues 94 and 129–135. This region is adjacent to the active site and has significant dynamic behavior on the μs—ms and ps—ns timescales. Correlation of chemical shift changes and mobility of these residues further suggest the importance of these residues in substrate recognition.