Abstract Saccharomyces cerevisiae accomplishes high rates of hexose transport. The kinetics of hexose transport are complex. The capacity and kinetic complexity of hex- ose transport in yeast are reflected in the large number of sugar transporter genes in the genome. Twenty hexose transporter genes exist in S. cerevisiae. Some of these have been found by genetic means; many have been dis- covered by the comprehensive sequencing of the yeast genome. This review codifies the nomenclature of the hexose transporter genes and describes the sequence ho- mology and structural similarity of the proteins they en- code. Information about the expression and function of the transporters is presented. Access to the sequences of the genes and proteins at three sequence databases is pro- vided via the World Wide Web. Key words Hexose transport · Glucose transport · Galactose transport · Genome sequence analysis · Telomere The obligate first step of sugar metabolism is sugar trans- port. In the yeast Saccharomyces cerevisiae, hexoses are delivered to cellular metabolism by facilitated diffusion across the plasma membrane. The rate of transport by cells that are fermenting rapidly can exceed 10 7 glucose molecules per cell per second. Transport has been inferred to be the rate-limiting step of glycolysis (Becker and Betz 1972; Gancedo and Serrano 1989); in the description of metabolic control analysis (Fell 1992), transport has a high degree of control on glycolytic flux (Cortassa and Aon 1993; Oehlen et al. 1994). The kinetic characteristics of hexose transport have been characterized by many investigators. However, the mole- cular basis of hexose transport is only beginning to be un- derstood. This is due in part to the intractibility of the hy- drophobic transport proteins to biochemical analysis, and in part to the genetic complexity of the hexose transport sys- tem in yeast. Now, with the complete sequence of the S. cerevisiae genome available for study, all of the candidate genes for the hexose transporters have been identified. The number of such candidates is surprisingly large. The roles of the plethora of sugar transporters is a fundamentally im- portant question in yeast biology. Do they differ in their ki- netic or functional characteristics? Are they differentially regulated in time or space? Or are they redundant, and is their number a consequence of genomic instability? The purpose of this review is to enumerate the hexose transporter gene family in yeast and to comment on some of the distinctive features of those genes and the proteins they encode. This review is intended to be topical rather than com- prehensive. Readers are referred to recent reviews on sugar transport in yeast (Bisson et al. 1993; Ciriacy and Reifenberger 1996; Lagunas 1993; Weusthuis et al. 1994) for more detailed discussions. Preliminary reports on the complexity of the HXT family of sugar transporter genes have been published by André (1995) and by Goffeau and co-workers (Nelissen et al. 1995). The tables and figures presented in this text are supplemented by tables and fig- ures that are available via World Wide Web (http://sci- ence.springer.de). Links from this server will lead the in- terested reader to the sequences of the genes and proteins at the Saccharomyces Genome Database, the Martinsried Institute of Protein Science, and the Yeast Protein Data- base. References to figure and table numbers of the sup- plementary materials available via World Wide Web are indicated with a “W.” Arthur L. Kruckeberg The hexose transporter family of Saccharomyces cerevisiae Arch Microbiol (1996) 166 : 283–292 © Springer-Verlag 1996 Received: 24 June 1996 / Accepted: 29 July 1996 MINI-REVIEW Dedicated in memory of Professor Michael Ciriacy Supplementary material Further details (Tables W1–W3 and Figs. W1–W4) have been deposited in electronic form and can be obtained from http://science.springer.de/archmicro/am.htm A. L. Kruckeberg Department of Biological Chemistry, UCLA School of Medicine, CHS 33–257, 10833 Le Conte Avenue, Los Angeles, CA 90095–1737, USA Tel. +1-310-825-8363; Fax +1-310-206-5272 e-mail: kruckeba@biovx1.biology.ucla.edu