Ms. Finnin et al., THE DNA-BINDING DOMAIN OF THE MOTA TRANSCRIPTION FACTOR FROM BACTERIOPHAGE-T4 SHOWS STRUCTURAL SIMILARITY TO THE TATA-BINDING PROTEIN, Proceedings of the National Academy of Sciences of the United Statesof America, 91(23), 1994, pp. 10972-10976
The bacteriophage T4 middle-mode transcription factor MotA consists of
two domains of approximately equal size. The C-terminal domain has be
en shown to contain the DNA-binding elements of the molecule, and the
N-terminal domain appears to interact with RNA polymerase. A 12.5-kDa
fragment of the C-terminal domain (MotCF), comprising residues 105-211
of MotA, was found to be suitable for structural studies by NMR. The
H-1 and N-15 assignments have been made for MotCF by using two-dimensi
onal homonuclear and heteronuclear experiments. A secondary structure
has been determined which consists of a six-stranded antiparallel beta
-pleated sheet with three alpha-helical segments. The secondary struct
ure of MotCF has a clear similarity to one half of the eukaryotic TATA
-binding protein (TBP), which is an intramolecular diner. Therefore, M
otCF may be related to a monomeric ancestral protein of TBP. TBP binds
its target DNA in the minor groove by specific interactions with hydr
ophobic and aromatic residues on the exposed sheet surface of the prot
ein. Similar residues are also present on the beta-sheet surface of Mo
tCF, suggesting that it too binds DNA in the minor groove.