Expanding family

Sir-We have recently described1 a family of six fungal genes involved in mitosis and the regulation of RNA synthesis whose protein products have in common a repetitive sequence motif of 34 amino acids (tetratricopeptide repeat or TPR). In the new examples, the В submotif is maintained but there are different patterns of sequence conservation in A. We believe that TPR genes have evolved different functions based both on divergence of TPR sequences and also on the acquisition of separate, unrelated functional domains such as the targeting/ anchoring sequence in the Mt 70,000 outer mitochondrial membrane protein and the žeste-like domain in SSN6 (ref. 1). Boguski National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, USA Philip Hieter Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA Mark Goebl Department of Biochemistry, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA Roberts.