Functional characterisation and transcriptional regulation of the KIHEM12 gene from Kluyveromyces lactis

Cloning, sequencing and functional analysis of the Kluyveromyces lactis KlHEM12 gene and its upstream region are reported. The gene encodes for a protein that is highly homologous to uroporphyrinogen decarboxylases from different organisms and complements its mutation in Saccharomyces cerevisiae. Secondary structure prediction allows outlining a topology diagram which is compatible with a (beta/alpha)(8)-barrel structure. A K. lactis haploid strain carrying a null allele of KlHEM12 showed decreased growth in media not supplemented with hemin (ferriprotoporphyrin IX) and red-fluorescent colonies due to the accumulation of porphyrins. KlHEM12 expression was analysed by Northern blot and promoter fusion to the reporter lacZ gene. Transcription of this gene is not under heme or glucose repression and it is slightly induced by nonfermentable carbon sources through the Hap2/3/4/5 complex.