CLONING AND NUCLEOTIDE-SEQUENCE OF A GENE CONFERRING ABILITY TO GROW AT A LOW-TEMPERATURE ON SACCHAROMYCES-CEREVISIAE TRYPTOPHAN AUXOTROPHS

A gene conferring on yeast YNN140 the ability to grow at a low temperature was cloned and designated LTG3 (low temperature growth gene). Disruption of the LTG3 gene resulted in no growth at a low temperature. It was shown that the effect of the presence of the gene in multicopy was dependent on the strain. DNA sequencing analysis of the LTG3 gene revealed an open reading frame which can encode 592 amino acids. The deduced amino acid sequence of the protein was homologous with that of some amino acid permeases. Since the addition of a large amount Of L-tryptophan to YPAD medium enabled the YNN140 strain to grow at a low temperature, it is possible that a limiting step for YNN140 to grow at a low temperature is to take up tryptophan from the medium. A part of the nucleotide sequence of the cloned DNA containing the LTG3 gene coincided with that of the SUP3 gene, indicating that the LTG3 gene exists on chromosome XV.