ABSTRACT
This chapter determines whether chicken erythrocyte high-mobility group (HMG) proteins are capable of lowering the Tm of poly(dA-dT). It describes binding studies from which the authors obtain estimates of the affinities of HMG-E for single- and double-stranded DNAs and of the binding site sizes for the two types of DNA. HMG-E (as well as HMG-1 and -2) is believed to have three structural domains. Domains A and B are DNA-binding, sequence homologous, globular domains. The decrease in fluorescence can be used to generate a binding curve from which estimates of binding parameters can be extracted using a suitable model. The chapter suggests that light scattering from denatured protein at appropriate HMG-1-to-poly(dA-dT) ratios can contribute to a thermal denaturation curve in a way that the curve resembles a biphasic denaturation of the polynucleotide. The affinities of HMG-E and, by inference from DNA-cellulose chromatography, of HMG-1 and -2 for both forms of DNA at 0.2 M NaCl are not particularly high.
