NUCLEIC-ACID BINDING-PROPERTIES OF A HELIX STABILIZING NUCLEOID PROTEIN FROM THE THERMOACIDOPHILIC ARCHAEON SULFOLOBUS-ACIDOCALDARIUS THAT CONDENSES DNA INTO COMPACT STRUCTURES

Helix stabilising nucleoid protein (HSNP-C') from an acidothermophilic archaeon Sulfolobus acidocaldarius has been characterised with respec t to interaction with nucleic acids by gel retardation assay, binding to nucleic acid columns, fluorescence titrations and electron microsco py. The protein exists in solution as very large multimeric aggregates as indicated by cross-linking studies. The protein binds strongly and co-operatively to double stranded DNA. Electron microscopy of the com plexes of the protein with DNA shows compact structures suggesting tha t the protein condenses DNA.