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DTSTAMP:20260404T014057Z
UID:60001734d15da759246231@ist.ac.at
DTSTART:20210226T130000
DTEND:20210226T140000
DESCRIPTION:Speaker: Georg Hochberg\nhosted by Martin Loose\nAbstract: Why 
 does anything complicated exist in biology at all? Organisms contain many 
 structures\, from macroscopic organs down to the molecular machines that p
 ower cells\, that seem complex enough that they are unlikely to be the pro
 duct of random chance.Classically\, such features are thought to exist bec
 ause they help the organism survive better than it would without it. This 
 would allow purifying selection to preserve them against the constant hail
  of destructive mutations that occur every time genomes replicate. But at 
 the molecular scale\, there are many complex biochemical structures that h
 ave no apparent purpose: many protein complexes are built from units that 
 in theory should work just as well on their own.Yet they persist across th
 e eons. If not purifying selection for some useful function\, what protect
 s them from mutational destruction? Using ancestral sequence reconstructio
 n and biochemical characterization of resurrected proteins\, I will show h
 ow protein complexes can persist for long periods of time not because they
  are useful\, but because of a universal mutational ratchet. The ratchet m
 akes it nearly impossible for evolution to return to simpler biochemical f
 orms once a complex has evolved. I will then show unpublished work on a si
 milar ratchet at work in RuBisCo\, the enzyme that performs almost all CO2
 fixation on earth. I will recapitulate how RuBisCo acquired an accessory s
 ubunit that it quickly came to completely depend on for its function. This
  happened not because the interaction was useful\, but because it allowed 
 mutations to accumulate that would be very harmful in the absence of the i
 nteraction. This work suggests neutral processes can be a powerful force p
 reserving complexity at the molecular level
LOCATION:Online Event ()\, ISTA
ORGANIZER:mloose@ist.ac.at
SUMMARY:Georg Hochberg: Chance and purpose in the evolution of protein comp
 lexes
URL:https://talks-calendar.ista.ac.at/events/3050
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