Genome Mining of Non-Conventional Yeasts: Search and Analysis of  MAL  Clusters and Proteins.
Genomic clustering of functionally related genes is rare in yeasts and other eukaryotes with only few examples available. Here, we summarize our data on a nontelomeric  MAL  cluster of a non-conventional methylotrophic yeast  Ogataea  ( Hansenula )  polymorpha  containing genes for α-glucosidase MAL1, α-glucoside permease MAL2 and two hypothetical transcriptional activators. Using genome mining, we detected  MAL  clusters of varied number, position and composition in many other maltose-assimilating non-conventional yeasts from different phylogenetic groups. The highest number of  MAL  clusters was detected in  Lipomyces starkeyi  while no  MAL  clusters were found in  Schizosaccharomyces pombe  and  Blastobotrys adeninivorans . Phylograms of α-glucosidases and α-glucoside transporters of yeasts agreed with phylogenesis of the respective yeast species. Substrate specificity of unstudied α-glucosidases was predicted from protein sequence analysis. Specific activities of  Scheffersomyces  stipitis  α-glucosidases MAL7, MAL8, and MAL9 heterologously expressed in  Escherichia coli  confirmed the correctness of the prediction-these proteins were verified promiscuous maltase-isomaltases. α-Glucosidases of earlier diverged yeasts  L. starkeyi ,  B. adeninivorans  and  S. pombe  showed sequence relatedness with α-glucosidases of filamentous fungi and bacilli.
Viigand K, Põšnograjeva K, Visnapuu T, Alamäe T