Journal club next Sunday!

[Lindsay]

Hi all, sorry for my disappearance. I moved house and was too busy to
remember what day it was. Anyway, I'm back, and here's the paper I'll
be presenting on Sunday, January 22 at noon in room 377

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10724.html

Evolution of increased complexity in a molecular machine
Gregory C. Finnigan, Victor Hanson-Smith, Tom H. Stevens & Joseph
W. Thornton

Many cellular processes are carried out by molecular ‘machines’—
assemblies of multiple differentiated proteins that physically
interact to execute biological functions1, 2, 3, 4, 5, 6, 7, 8.
Despite much speculation, strong evidence of the mechanisms by which
these assemblies evolved is lacking. Here we use ancestral gene
resurrection9, 10, 11 and manipulative genetic experiments to
determine how the complexity of an essential molecular machine—the
hexameric transmembrane ring of the eukaryotic V-ATPase proton pump—
increased hundreds of millions of years ago. We show that the ring of
Fungi, which is composed of three paralogous proteins, evolved from a
more ancient two-paralogue complex because of a gene duplication that
was followed by loss in each daughter copy of specific interfaces by
which it interacts with other ring proteins. These losses were
complementary, so both copies became obligate components with
restricted spatial roles in the complex. Reintroducing a single
historical mutation from each paralogue lineage into the resurrected
ancestral proteins is sufficient to recapitulate their asymmetric
degeneration and trigger the requirement for the more elaborate three-
component ring. Our experiments show that increased complexity in an
essential molecular machine evolved because of simple, high-
probability evolutionary processes, without the apparent evolution of
novel functions. They point to a plausible mechanism for the evolution
of complexity in other multi-paralogue protein complexes.

[Lindsay]

don't forget! Journal Club today at 12.

Lindsay