... (1994) Acute intermittent porphyria: identificationand expression of exonic mutations in the hydrox-ymethylbilane synthase gene. An initiation codon mis-sense mutation in the housekeeping transcript ... p.Arg116Gln in the acceptor resi-due in the ion pair, reducing their ability to formionic interaction, have previously been found in AIP patients [28,29]. The effect of the new mutationp.Glu250Asp ... HMBS indicating the positions of the mutations observed in the patients. The N-, central andC-domains are shown in silver, blue and green, respectively; the positions of the mutated amino acids...