Two helix DNA binding motif of CAP found in lac repressor and gal repressor.
AUTOR(ES)
Weber, I T
RESUMO
Comparison of both the DNA and protein sequences of catabolite gene activator protein (CAP) with the sequences of lac and gal repressors shows significant homologies between a sequence that forms a two alpha-helix motif in CAP and sequences near the amino terminus of both repressors. This two-helix motif is thought to be involved in specific DNA sequence recognition by CAP. The region in lac repressor to which CAP is homologous contains many i-d mutations that are defective in DNA binding. Less significant sequence homologies between CAP and phage repressors and activators are also shown. The amino acid residues that are critical to the formation of the two-helix motif are conserved, while those residues expected to interact with DNA are variable. These observations suggest the lac and gal repressors also have a two alpha-helix structural motif which is involved in DNA binding and that this two helix motif may be generally found in many bacterial and phage repressors. We conclude that one major mechanism by which proteins can recognize specific base sequences in double stranded DNA is via the amino acid side chains of alpha-helices fitting into the major groove of B-DNA.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=320853Documentos Relacionados
- Amino acids determining operator binding specificity in the helix-turn-helix motif of Tn10 Tet repressor.
- DNA supercoiling changes the spacing requirement of two lac operators for DNA loop formation with lac repressor.
- Water release associated with specific binding of gal repressor.
- Lac repressor with the helix-turn-helix motif of lambda cro binds to lac operator.
- Structure of the DNA-binding region of lac repressor inferred from its homology with cro repressor.
