Fig. 6. Mmy encodes the Drosophila UDP-N-acetylglucosamine pyrophosphorylase. (A) Genome organisation of mmy, showing the exons (grey boxes) used in each of the two mmy transcripts RA and RB. Start and stop codons are marked in red and green, respectively. The two EMS-induced mmy mutations mmy^IK63 and mmy^IL07 introduce single mis-sense mutations in the third common exon, whereas P-element KG04349 is inserted 5' to the ATG of RA, and P-element KG08617 disrupts the second intron of both RA and RB. (B) Sequence alignment of the Mmy protein with its orthologues in yeast, human and Aedes. The mis-sense mutations in mmy^IK63 and mmy^IL07 cause substitution of conserved amino acids as indicated above the sequence. The extra 37 amino acids in isoform A are underlined and do not show homology to Mmy orthologues. (C) Illustration of the biochemical reaction catalysed by Mmy and the main biological processes that require the Mmy product.