Biochemistry

A Party of 10, Again

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Science  16 Jun 2006:
Vol. 312, Issue 5780, pp. 1575
DOI: 10.1126/science.312.5780.1575a

Applying proteomic technologies has made it possible to catalog the complement of proteins expressed in a cell or a tissue, and experimental and computational analyses have coupled proteins to their partners in social networks of metabolic and regulatory connectedness—an interactome. Partying (multiple contacts simultaneously) and dating (one at a time) have been proposed as classifying behaviors, and probing the interaction surfaces may help sort out which is which.

Hernández et al. have used tandem affinity purification and mass spectrometry to map the 10 distinct subunits of the yeast exosome, a complex involved in RNA processing. Of the three subunits with RNA-binding motifs (Csl4, Rrp40, and Rrp4), Csl4 showed up in substoichiometric quantities and hence was tagged so as to pull out only the complete 10-subunit species. Destabilizing the intraexosome interactions with dimethylsulfoxide, followed by mass spectrometry, established the composition and neighbor relationships for the six-subunit ring; likewise, all three RNA-binding proteins could be placed on the same face of the ring, with the largest subunit, the Dis3 RNase, on the other side. — GJC

EMBO Rep. 10.1038/sj.embor.7400702 (2006).

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