Conserved pathways within bacteria and yeast as revealed by global protein network alignment

doi:10.1073/pnas.1534710100

Conserved pathways within bacteria and yeast as revealed by global protein network alignment

^*Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142; and ^†International Computer Science Institute, 1947 Center Street, No. 600, Berkeley, CA 94704

Contributed by Richard M. Karp, July 25, 2003

Abstract

We implement a strategy for aligning two protein–protein interaction networks that combines interaction topology and protein sequence similarity to identify conserved interaction pathways and complexes. Using this approach we show that the protein–protein interaction networks of two distantly related species, Saccharomyces cerevisiae and Helicobacter pylori, harbor a large complement of evolutionarily conserved pathways, and that a large number of pathways appears to have duplicated and specialized within yeast. Analysis of these findings reveals many well characterized interaction pathways as well as many unanticipated pathways, the significance of which is reinforced by their presence in the networks of both species.

Footnotes

↵ ‡ To whom correspondence should be sent at the present address: University of California at San Diego, Department of Bioengineering, 9500 Gilman Drive, La Jolla, CA 92093. E-mail: trey{at}bioeng.ucsd.edu.
Abbreviation: MAPK, mitogen-activated protein kinase.
↵ § The term “pathway” has been used broadly within various molecular biological contexts to refer to biochemical reaction chains, signal transduction cascades, gene regulatory systems, or other sequences of biomolecular events. Here a pathway refers to a sequence of protein–protein interactions forming a connected path in the network.
↵ ¶ We have also explored methods for identifying conserved subnetworks as opposed to linear paths (see Fig. 7, which is published as supporting information on the PNAS web site); choosing which approach is most desirable remains an open problem and depends on issues of computational efficiency and whether protein complexes or sequential pathways such as signal transduction or regulatory cascades are of highest interest.