Functional Roles of Highly Conserved Amino Acid Sequence Motifs A and C in Solute Transporters of the Major Facilitator Superfamily

Abstract

The biological membrane covers all living cells and provides an effective barrier against the passage of biologically important water-soluble solutes. This natural passage barrier is essentially overcome with the use of integral membrane proteins known as solute transporters. These transport systems translocate solutes across the membrane such as in the case of bacterial drug and multidrug resistance efflux pumps. One of the largest groups of transporters is referred to as the major facilitator superfamily. This group contains secondary active transporters such as symporters and antiporters and passive transporters such as uniporters. The transporters within the major facilitator superfamily share conserved structures and primary amino acid sequences. In particular, several highly conserved amino acid sequence motifs have been discovered and studied extensively, providing substantial evidence for their critical functional roles in the transport of solutes across the membrane.