Nucleic Acids Research, Vol 24, Issue 21 4249-4255, Copyright © 1996 by Oxford University Press
K Ikehara, F Amada, S Yoshida, Y Mikata and A Tanaka
Base compositions were examined at every position in codons of more than 50
genes from taxonomically different bacteria and of the corresponding
antisense sequences on the bacterial genes. We propose that the nonstop
frame on antisense strand [NSF(a)] of GC-rich bacterial genes is the most
promising sequence for newly-born genes. Reasons are: (i) NSF(a) frequently
appears on the antisense strand of GC-rich bacterial genes; (ii) base
compositions at three positions in the codon are nearly symmetrical between
the gene having around 55% GC content and the corresponding NSF(a); (iii)
amino acid compositions of actual proteins are also similar to those of
hypothetical proteins from the GC-rich NSF(a); and (iv) proteins from
NSF(a) of 60% or more GC content are flexible enough to adapt to various
molecules encountered as novel substrates, due to the high glycine content.
To support our proposition, using a computer we generated hypothetical
antisense sequences with the same base compositions as of NSF(a) at each
base position in the codon, and examined properties of resulting proteins
encoded by the imaginary genes. It was confirmed that NSF(a) of GC-rich
gene carrying about 60% GC content is competent enough for a newly-born
gene.
ARTICLES
A possible origin of newly-born bacterial genes: significance of GC- rich nonstop frame on antisense strand
Department of Chemistry, Faculty of Science, Nara Women's University, Kita-uoya Nishi-machi, Japan. ikehara@cc.nara-wu.ac.jp
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