Nucleic Acids Research, Vol 25, Issue 14 2847-2853, Copyright © 1997 by Oxford University Press
AG Stepchenko, NN Luchina and EV Pankratova
The best target of POU proteins (Oct-1, Oct-2) is an octamer sequence
ATGCAAAT. POU proteins also recognize, with weaker affinity, the TAAT- like
targets of another group of regulatory factors, the homeoproteins. Up to
now, it has not been known why Cys50 of the POUHdomain is absolutely
conserved in contrast to that in homeoproteins. To assess the importance of
Cys50 in determining the binding specificity of POU proteins, all possible
amino acids were substituted for Cys at position 50, and the resulting
mutants were tested with probes containing octamer (ATGCAAATNN) or
homeospecific binding sites. Only the wild-type POU was shown to adequately
discriminate between the octamer and homeospecific sites, and the protein
affinity was only slightly affected by the nucleotide sequence flanking the
octamer at the 3'-end. Any amino acid substitution at position 50 resulted
in the mutant protein binding efficiently both to the octamer and the
TAAT-like sequences. Moreover, in this case the 3'-flanking sequences
influenced the binding to a much greater extent.
ARTICLES
Cysteine 50 of the POU H domain determines the range of targets recognized by POU proteins
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilov str., 117984 Moscow, Russia. pol@genomii.eimb.rssi.ru
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