Abrie JA, Gonzalez A, Strauss E, Arino J

The Saccharomyces cerevisiae Hal3 protein is a moonlighting protein, able to function both as an inhibitory subunit of the Ppz1 protein phosphatase and as a constituent protomer of an unprecedented heterotrimeric phosphopantothenoylcysteine decarboxylase (PPCDC), the third enzyme of the CoA biosynthetic pathway. We initiated here the dissection of the structural ...

Read More

elements required for both disparate cellular tasks by using a combination of biochemical and genetic approaches. We show that the conserved Hal3 core (the PPCDC domain) is necessary for both functions, as determined by in vitro and in vivo assays. The Hal3 N-terminal domain is not functional by itself, although in vitro experiments indicate that when this domain is combined with the core it has a relevant function in Hal3's heteromeric PPCDC activity. Both the N-terminal and the acidic C-terminal domain also appear to be important for Hal3's Ppz1 regulatory function, although our results indicate that the C-terminal domain fulfils the key role in this regard. Finally, we show that the introduction of two key Asn and Cys residues, essential for monofunctional PPCDC activity but absent in Hal3, is not sufficient to convert it to such a homomeric PPCDC, and that additional modifications of Hal3's PPCDC domain aimed at increasing its resemblance to known PPCDC also fails to introduce this activity. This suggests that Hal3 has undergone significant evolutionary drift from ancestral PPCDC proteins. Taken together, our work highlights specific structural determinants that could be exploited for full understanding of Hal3's cellular functions.

Date: Nov. 29, 2011

View in: Pubmed Google Scholar

126637