I would like to point out the following paper (just published):
Berg, O.G. 1992. PNAS 89:7501-7505
The evolutionary selection of DNA base-pairs in gene-regulatory
binding sites.
The abstract reads in part:
(hopefully the chief editor of PNAS won't get mad at me --
he's 1 floor up!)
"The DNA base-pair sequences that serve as gene-regulatory sites have been
selected to provide an appropriate functional binding for a particular
protein. In most cases, the function depends on the binding
probability, which can be influenced both by the binding strength
and by the abundance of the protein in the cell. As a consequence,
the same function can be achieved with strong binding sites and
a small amount of protein or weak binding sites and a strong
amount of protein. However, increasing the protein burden will
decrease the growth rate of the cells. Thus, for maximal growth
the protein levels should be as low as possible and the binding
correspondingly strong. On the other hand, sequences with a
weaker binding can be formed in many more ways and are, therefore,
more probable, and random mutations are more likely to produce them.
Thus the selection pressure against an increased protein burden
can be balanced against the random mutational drift in the recognition
sequences...
Keith Robison
Harvard University
Department of Cellular & Developmental Biology
Department of Genetics / HHMI
robison at ribo.harvard.edu
