Efficient expression, purification and crystallisation of two hyperthermostable enzymes of histidine biosynthesis

Enzymes from hyperthermophiles can be efficiently purified after expression in mesophilic hosts and are well-suited for crystallisation attempts. Two enzymes of histidine biosynthesis from Thermotoga maritima, N'-((5 '-phosph oribosyl)formimino)-5-aminoimidazol-4-carboxamid ribonucleotide isomerase a nd the cyclase moiety of imidazoleglycerol phosphate synthase, were overexp ressed in Escherichia coli, both in their native and seleno-methionine-labe lled forms, purified by heat precipitation of host proteins and crystallise d. N'-((5'-phosphoribosyl)-formimino)-5-aminoimidazol-4-carboxamid ribonucl eotide isomerase crystallised in four different forms, all suitable for X-r ay structure solution, and the cyclase moiety of imidazoleglycerol phosphat e synthase yielded one crystal form that diffracted to atomic resolution. T he obtained crystals will enable the determination of the first three-dimen sional structures of enzymes from the histidine biosynthetic pathway. (C) 1 999 Federation of European Biochemical Societies.