Fig. 6

The interface between coupling helices and NBDs of Mycobacterium tuberculosis carbohydrate ABC transporters. A Structural model of a carbohydrate transporter showing the dimers of TMDs (pale blue and blue) and NBDs (cyan and deep cyan). The two coupling helices from each monomer are colored in green and red, respectively, and the NBD region that faces the helices is highlighted in a grey box. (I) and (II) Local amino acid sequence alignments of TMDs and NBDs, respectively. Coupling helices are colored as in the structural model. Sequences of the E. coli MalK and B. subtilis MsmX NBDs were included in the alignment for comparison. Residues of the interface between MalK and MalF/G are shown in red underlined and those that determine promiscuity in MsmX are in bold. B Electrostatic potential of TMDs coupling helices and NBDs shown as surface. The area in black line highlights the position of the interaction. Blue: positive, red: negative, grey: neutral. C Structure of the NBD dimers in surface showing the two monomers and the regions (area in black line) that might interact with coupling helices. The NBD structures are also shown in cyan surface with the putative residues important in the interaction in red