Fig. 1. Ductin basics. A.i: Ductin (purple) is part of the transmembrane proton transporting V0 domain of the HV-ATPase (Entrez Gene Name: ATPase, Htransporting, lysosomal 16 kD, V0 subunit c; drawing after Hinton et al., 2009). The V0 domain includes a hexamer comprising four ductin monomers plus two similar proteins, c0 and c00. Protons () enter subunit a on the cytoplasmic side (top thin black arrow) and are picked up by a glutamic acid (E140, green) in TM4 of ductin. After rotation (curved, open arrow), ductin delivers the proton to another site in subunit a, which releases it to the other side of the membrane (lower thin black arrow). A.ii: The HV-ATPase acidifies the lumen of intracellular vesicles, including lysosomes. In some cells, it is present in the plasma membrane. B: The amino acid sequence of ductin is very highly conserved. The four transmembrane domains are indicated by the purple background; the proton binding E is indicated by the green arrowhead. The top sequence is Xenopus ductin, the next is xduct-noTM4. Below that are the cow, chick, mouse, rat, human, and zebrafish sequences.
Image published in: Vandenberg LN et al. (2011)
Copyright © 2011. Image reproduced with permission of the Publisher, John Wiley & Sons.
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