Functional analysis of yeast gene families involved in metabolism of vitamins B 1 and B 6

In order to clarify their physiological functions, we have undertaken a characterization of the three‐membered gene families SNZ1–3 and SNO1–3 . In media lacking vitamin B 6 , SNZ1 and SNO1 were both required for growth in certain conditions, but neither SNZ2, SNZ3, SNO2 nor SNO3 were required. Copies 2 and 3 of the gene products have, in spite of their extremely close sequence similarity, slightly different functions in the cell. We have also found that copies 2 and 3 are activated by the lack of thiamine and that the Snz proteins physically interact with the thiamine biosynthesis Thi5 protein family. Whereas copy 1 is required for conditions in which B 6 is essential for growth, copies 2 and 3 seem more related with B 1 biosynthesis during the exponential phase. Copyright © 2002 John Wiley & Sons, Ltd.