The HMG box domain of the testis determining factor, SRY, includes a b
asic amphiphilic sequence common to calmodulin (CaM) binding proteins,
By affinity chromatography, native gel electrophoresis and fluorescen
ce spectroscopy, we show the calcium-dependent binding of SRY to CaM,
Binding occurs via the HMG box and an SRY peptide of residues 57-80 bi
nds CaM like the intact domain, SRY/CaM complex formation is specifica
lly inhibited by the SRY DNA binding site sequence, AACAAT, but not a
mutated sequence, Fluorescence spectra of the SRY/CaM complex indicate
1:1 stoichiometry and that binding is accompanied by a conformational
change in SRY, The A domain of HMG1 also binds CaM and me propose tha
t CaM binding is a property of the wider HMG box family, including SOX
and TCF/LEF proteins, These results suggest that CaM may regulate the
DNA binding activity of HMG box transcription factors.