<p>Bacterial high affinity transport systems are involved in active transport of solutes across the cytoplasmic membrane. The protein components of these traffic systems include one or two transmembrane protein components, one or twomembrane-associated ATP-binding proteins and a high affinity periplasmic solute-binding protein. In Gram-positive bacteria which are surrounded by a single membrane and have therefore no periplasmic region the equivalent proteinsare bound to the membrane via an N-terminal lipid anchor. These homologue proteins do not play an integral role in the transport process per se, but probably serve as receptors to trigger or initiate translocation of the solute through the membrane by binding to external sites of the integral membrane proteins of the efflux system. In addition at least some solute-binding proteins function in the initiation of sensory transduction pathways.</p><p>On the basis of sequence similarities, the vast majority of these solute-binding proteins can be grouped [<cite idref="PUB00003610"/>] into eight families of clusters, which generally correlate with the nature of the solute bound. Family 1 currently includes the periplasmic proteins maltose/maltodextrin-binding proteins of enterobacteriaceae (gene malE) [<cite idref="PUB00003346"/>] and <taxon tax_id="1313">Streptococcus pneumoniae</taxon> malX; multiple oligo-saccharide binding protein of <taxon tax_id="1309">Streptococcus mutans</taxon> (gene msmE); <taxon tax_id="562">Escherichia coli</taxon> glycerol-3-phosphate-binding protein; <taxon tax_id="615">Serratia marcescens</taxon> iron-binding protein (gene sfuA) and the homologous proteins (gene fbp) from <taxon tax_id="727">Haemophilus influenzae</taxon> and Neisseria; and E. coli thiamine-binding protein (gene tbpA).</p> Bacterial extracellular solute-binding family 1, conserved site