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Re- Evolutionary tree of *all* proteins

RYBICKI, ED ED at molbiol.uct.ac.za
Sun Oct 16 03:49:50 EST 1994


> From:          biocukm at okway.okstate.edu (Ulrich Melcher)

> I think we (Lartey, Voss and myself, ms in preparation) may have 
come across a 
> case where convergent sequence evolution has occurred during the 
evolution of 
> the ribgrass mosaic virus subgroup of tobamoviruses.  In their RNA 
genomes the 
> movement and coat protein cistrons overlap for 25 codons.  In 
other 
> tobamoviruses there is no overlap or a shorter overlap.  The 
ancestral cistron 
> in the overlap region can be deduced to be the coat protein one.  
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Er...why?  Is it not possibly an N-terminal extension of the CP?  
How "homologous" are those regions of the tobamovirus CPs?  Enough 
to say that this has not occurred?

...I think that is what is meant by convergent 
> sequence evolution.  The situation will certainly complicate 
phylogenies based 
> on movement protein amino acid sequences since all alignment 
algorithms will put 
> the C-termini together in some fashion, even though they are 
encoded by non-
> homologous nucleotides.

This is definitely true IF it is the case...so, for all rules there 
has to be an exception!

  _________________________________________________________________
 | Ed Rybicki, PhD          |         Well, I tip my hat           |
 | (ed at micro.uct.ac.za)     |      To the new constitution         |
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 | University of Cape Town  |  Then I get on my knees and pray     |
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 | 7700, South Africa       |                                      |
 | fax: xx27-21-650 4023    |      - Pete Townshend, 1972          |
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