7-kb MTT1 versions from these strains did not (see Fig. 3 for representative clones). None of the transformants with the 2.4- and 2.7-kb versions of MAL31 from all four lager strains started growing quicker on maltotriose in the presence of antimycin A than A15 or A15 with the control plasmid (see Fig. 3 for representative clones). Previously, we showed that MTT1alt,
which encodes an Mtt1-type maltose transporter with an artificially altered C-terminus, was able to restore the rapid growth of A15 on maltotriose with antimycin A even on a low-copy CEN plasmid (Dietvorst et al., 2005). Therefore, we also tested this ability of the small MTT1 isolate Selleckchem U0126 from A15. After the introduction of a centromere, CEN4, the multicopy plasmid with the A15 2.4-kb isolate was unable to restore rapid growth (data not shown). We have not tested whether the 2.4-kb MTT1 isolates from other strains behave similarly. However, given the identical sequences of these genes, it is highly likely that single copies of these genes will not restore the rapid growth of A15 on maltotriose in the presence of antimycin A either. From each of the 2.7-kb versions of MTT1 from strains WS34/70 and BS07 as well as from the 2.4-kb versions of MTT1 from strains A15, BS01 and BS07, one isolate was sequenced. Sequence analysis AC220 supplier confirmed the previous classification of the isolates based on the specific primer sets (Fig. 2) in MTT1-like
and MAL31-like genes. For further analysis, the sequences of seven previously isolated clones were included. The ORFs of all seven MTT1 isolates are highly similar to the Saccharomyces pastorianus MTY1 gene (Salema-Oom et al., 2005) and identical to each other, with the exception of WS34/70 2.7 kb (clone 6) (see Supporting Information, Fig. S1). This isolate encodes a predicted protein that has four different amino acid residues, at positions 58, 247, 265 and 283, which are the same as the residues at the corresponding positions in the MAL31 gene. The predicted proteins of the five MAL31 genes are also highly similar to each
other with a few scattered deviating medroxyprogesterone amino acids, with the clear exception of BS07 2.7 kb (clone 4), which is identical to the MTT1 isolates. The MTT1- and MAL31-encoded proteins are c. 90% similar to each other. Motif searches using prosite showed two motifs in the MTT1 gene products: a sugar transport motif (PS00217) at residues 210–235 and a polygalacturonase motif (PS00502) at residues 446–459. As two amino acid residues of the latter motif are different in this region of the MAL31-encoded proteins, the MAL31 gene product may lack a polygalacturonase motif. The upstream sequences of all 12 genes contain in the first 425 bp from the ATG start site, −1 to −425, only 5-bp differences, which occur scattered in 1, 2 or 3 of the sequences (see Fig. S2). The main differences between the genes are present in the further upstream sequences. The promoters of the long 2.