Figure 15-10. The four classes of ATP-powered transport proteins.

Figure 15-10The four classes of ATP-powered transport proteins

P-class pumps are composed of two different polypeptides, α and β, and become phosphorylated as part of the transport cycle. The sequence around the phosphorylated residue, located in the larger α subunits, is homologous among different pumps. F-class and V-class pumps do not form phosphoprotein intermediates. Their structures are similar and contain similar proteins, but none of their subunits are related to those of P-class pumps. All members of the large ABC superfamily of proteins contain four core domains: two transmembrane (T) domains and two cytosolic ATP-binding (A) domains that couple ATP hydrolysis to solute movement. These core domains are present as separate subunits in some ABC proteins (depicted here), but are fused into a single polypeptide in other ABC proteins. [Adapted from C. H. Higgins, 1995, Cell 82:693; P. Zhang et al., 1998, Nature 392:835; Y. Zhou, T. Duncan, and R. Cross, 1997, Proc. Nat’l. Acad. Sci. USA 94:10583; and T. Elston, H. Wang, and G. Oster, 1998, Nature 391:510.]

From: Section 15.5, Active Transport by ATP-Powered Pumps

Cover of Molecular Cell Biology
Molecular Cell Biology. 4th edition.
Lodish H, Berk A, Zipursky SL, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

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