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This Week in Science: Feb 19, 2010

In Science this week, researchers describe their determination that N-terminally (Nt) acetylated Met residue could act as a degradation signal (degron), targeted by the Doa10 ubiquitin ligase, in the yeast Saccharomyces cerevisiae. They also show that Doa10 also recognized the Nt-acetylated alanaine, valine, serine, threonine, and cysteine residues. “Several examined proteins of diverse functions contained these N-terminal degrons, termed AcN-degrons, which are a prevalent class of degradation signals in cellular proteins,” the team writes. They note that more than 50 percent of proteins in S. cerevisiae and 80 percent of proteins in human cells are Nt-acetylated.

In Science Translational Medicine, a team of researchers from the University of California, San Francisco, and their colleagues report their finding that S-nitrosoglutathione reductase (GSNOR) deficiency may promote human hepatocellular carcinoma (HCC) through dysregulated S-nitrosylation. The UCSF-led team found reduced GSNOR abundance and activity in approximately 50 percent of patients with HCC. They also determined that “GSNOR-deficient mice were very susceptible to spontaneous and carcinogen-induced HCC.”

A team of international researchers report that lysine acetylation is a prevalent modification in enzymes that catalyze intermediate metabolism in Science this week. Shimin Zhao of Fudan University in Shanghai, China, and colleagues compared acetylated proteins against the total liver proteome and found that enzymes that participate in intermediate metabolism were preferentially acetylated. “Our study and others extend the scope of cell regulation by lysine acetylation to an extent comparable to that of other major posttranslational modifications such as phosphorylation and ubiquitination,” they write.

Srivatsan Raman of the University of Washington, Seattle, and colleagues describe their method for determining the structure of larger proteins using NMR and backbone-only data. Raman et al. write that the necessary side-chain resonance assignment associated with traditional NMR approaches is labor intensive and prone to error. Their new method, they write, “is not hindered by the deuteration required to suppress nuclear relaxation processes for proteins greater than 15 kilodaltons and should enable routine NMR structure determination for larger proteins.”