Structure of the HMG box motif in the B-domain of HMG1.
The conserved, abundant chromosomal protein HMG1 consists of two highly homologous, folded, basic DNA-binding domains, each of approximately 80 amino acid residues, and an acidic C-terminal tail. Each folded domain represents an 'HMG box', a sequence motif recently recognized in certain sequence-specific DNA-binding proteins and which also occurs in abundant HMG1-like proteins that bind to DNA without sequence specificity. The HMG box is defined by a set of highly conserved residues (most distinctively aromatic and basic) and appears to define a novel DNA-binding structural motif. We have expressed the HMG box region of the B-domain of rat HMG1 (residues 88-164 of the intact protein) in Escherichia coli and we describe here the determination of its structure by 2D 1H-NMR spectroscopy. There are three alpha-helices (residues 13-29, 34-48 and 50-74), which together account for approximately 75% of the total residues and contain many of the conserved basic and aromatic residues. Strikingly, the molecule is L-shaped, the angle of approximately 80 degrees between the two arms being defined by a cluster of conserved, predominantly aromatic, residues. The distinctive shape of the HMG box motif, which is distinct from hitherto characterized DNA-binding motifs, may be significant in relation to its recognition of four-way DNA junctions.
Weir
H M
HM
Department of Biochemistry, University of Cambridge, UK.
Kraulis
P J
PJ
Hill
C S
CS
Raine
A R
AR
Laue
E D
ED
Thomas
J O
JO
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000648:ultrastructure*; D006609:High Mobility Group Proteins / Q000648:ultrastructure*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000648:ultrastructure; D016415:Sequence Alignment
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins