Persistence of separate mitochondrial genome

Andrew Gyles syzygium at alphalink.com.au
Mon Sep 18 18:19:46 EST 2000

Race et al examined the argument that some of the proteins of
organelles 'are too hydrophobic to be imported across the double
membranes surrounding plastids and mitochondria' and cited an apparent
disproof of it, though not an entirely convincing one, involving the
large subunit of Rubisco.

The gene for this subunit is located in the chloroplast of tobacco. The
protein it encodes is highly hydrophilic, and therefore, they say,
ought to be in the nucleus. But that is hardly a disproof of the
hydrophobicity argument!

The Race article was cited earlier in this discussion by Mark Dowton
and Holger Hupfer. Mark Dowton summarised its support for Allen's
hypothesis that the synthesis of bioenergetic membranes must be tightly
regulated by the redox potentials generated by electron transport and
energy coupling, to minimise the unavoidable side effects of electron
transport and their deadly consequences for the cell. Therefore the
genes coding for the proteins of these membranes must be located in the

It is a persuasive argument, but it implies that these proteins must
have a short lifetime in the membrane, so that their concentrations can
be quickly controlled by variations in the rate of synthesis.

Andrew Gyles

In article <8q5ecu$6g8$1 at mercury.hgmp.mrc.ac.uk>,
  Daniel B Davison <Daniel.Davison at bms.com> wrote:
> Hi all,
> I thought I remembered discussion from ~25 years ago that the main
reason for the maintenance of
> mitochondrial genomes were that the proteins encoded by mtDNA were
extremely hydrophobic. Under this
> hypothesis, they had minimal chances of crossing the cytoplasm and
multiple membrances. mtDNA ensured that
> the proteins were made at the site they were needed.
> Thanks,
> dan davison

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