MODELING THE 2-KINASE DOMAIN OF 6-PHOSPHOFRUCTO-2-KINASE FRUCTOSE-2,6-BISPHOSPHATASE ON ADENYLATE KINASE/

Simultaneous multiple alignment of available sequences of the bifuncti onal enzyme phosphofructo-2-kinase/fructose-2,6-bisphosphatase reveale d several segments of conserved residues in the 2-kinase domain. The s equence of the kinase domain was also compared with proteins of known three-dimensional structure. No similarity was found between the kinas e domain of 6-phosphofructo-2-kinase and 6-phosphofructo-1-kinase. Thi s questions the modelling of the 2-kinase domain on bacterial 6-phosph ofructo-1-kinase that has previously been proposed [Bazan, Fletterick and Pilkis (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 9642-9646]. Howeve r, sequence similarities were found between the 2-kinase domain and se veral nucleotide-binding proteins, the most similar being adenylate ki nase. A structural model of the 2-kinase domain based on adenylate kin ase is proposed. It accommodates all the results of site-directed muta genesis studies carried out to date on residues in the 2-kinase domain . It also allows residues potentially involved in catalysis and/or sub strate binding to be predicted.