DNA-BINDING, NUCLEOTIDE-BINDING, TRANSCRIPTION REGULATION, BERYLLIUM FLUORIDE PHOSPHORYLATION MIMIC, HUPR, ACTIVATOR, CYTOPLASM, ATP-BINDING, TWO-COMPONENT REGULATORY SYSTEM, TRANSCRIPTION, PHOSPHOPROTEIN, RESPONSE REGULATOR 2VUI CRYSTAL STRUCTURE OF THE HUPR RECEIVER DOMAIN IN INHIBITORY PHOSPHO-STATE