HMG-box

In molecular biology, the HMG-box (high mobility group box) is a protein domain which is involved in DNA binding.^[1] The domain is composed of approximately 75 amino acid residues that collectively mediate the DNA-binding of chromatin-associated high-mobility group proteins. HMG-boxes are present in many transcription factors and chromatin-remodeling complexes, where they can mediate non-sequence or sequence-specific DNA binding.^[2]

HMG (high mobility group) box
NMR structure of the HMG-box domain of the LEF1 protein (rainbow colored, N-terminus = blue, C-terminus = red) complexed with DNA (brown) based on the PDB: 2LEF​ coordinates.
Identifiers
Symbol	PF00505
Pfam	PF00505
Pfam clan	CL0114
ECOD	190.1.1
InterPro	IPR009071
SCOP2	1hsm / SCOPe / SUPFAM
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary PDB 1aab​, 1cg7​, 1ckt​, 1e7j​, 1gt0​, 1hme​, 1hmf​, 1hry​, 1hrz​, 1hsm​, 1hsn​, 1i11​, 1j3x​, 1j46​, 1j47​, 1j5n​, 1k99​, 1lwm​, 1nhm​, 1nhn​, 1o4x​, 1qrv​, 1s9m​, 1sx9​, 1v64​, 1wgf​, 1wxl​, 2crj​, 2cs1​, 2lef​

Structure

The structure of the HMG-box domain contains three alpha helices separated by loops (see figure to the right).^[3]

Function

HMG-box containing proteins only bind non-B-type DNA conformations (kinked or unwound) with high affinity.^[1] HMG-box domains are found in some high mobility group proteins, which are involved in the regulation of DNA-dependent processes such as transcription, replication, and DNA repair, all of which require changing the conformation of chromatin.^[3] The single and the double box HMG proteins alter DNA architecture by inducing bends upon binding.^[4][5]