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At least one of them resulted from frame shit mutation on a strand of repetitive DNA sequence which did not code for functional protein, my understanding.
"the nylB group comes from a frameshift of an internally repetitious gene (so not surprisingly it is novel)"
The one came from frame shit mutation should not have homologous since it is novel. If you are interested, check the following links for detailed discussion:
http://www.nmsr.org/nylon.htm
http://www.talkorigins.org/origins/postmonth/apr04.html
original article on PNAS:
Proc. Natl. Acad. Sci. USA
Vol. 81, pp. 2421-2425, April 1984
Evolution
Birth of a unique enzyme from an alternative reading frame of the
preexisted, internally repetitious coding sequence
(oligomeric repeats/nylon oligomer degrading enzymes)
SUSUMU OHNO
Beckman Research Institute of The City of Hope, Duarte, CA 91010
Contributed by Susumu Ohno, January 4, 1984
ABSTRACT The mechanism of gene duplication as the
means to acquire new genes with previously nonexistent functions
is inherently self limiting in that the function possessed
by a new protein, in reality, is but a mere variation of the
preexisted theme. As the source of a truly unique protein, I
suggest an unused open reading frame of the existing coding
sequence. Only those coding sequences that started from oligomeric
repeats are likely to retain alternative long open reading
frames. Analysis of the published base sequence residing in the
pOAD2 plasmid of Flavobacterium Sp. K172 indicated that the
392-amino acid-residue-long bacterial enzyme 6-aminohexanoic
acid linear oligomer hydrolase involved in degradation of
nylon oligomers is specified by an alternative open reading
frame of the preexisted coding sequence that originally specified
a 472-residue-long arginine-rich protein.
[ 本帖最後由 blackcurtain 於 2008-1-5 04:00 編輯 ] |
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