Energy use by biological protein transport pathways. Trends Biochem. Sci

The targeting of proteins into and across biological membranes to their correct cellular locations is mediated by a variety of transport pathways. These systems must couple the thermodynamically unfavor-able processes of substrate translocation and inte-gration with the expenditure of metabolic energy, using the free energy of ATP and GTP hydrolysis and/or a transmembrane protonmotive force. Several recent advances in our knowledge of the structure and func-tion of these transport systems have provided insights into the mechanisms of energy transduction, force generation and energy use by different protein trans-port pathways. The targeting of soluble and membrane-bound proteins to their correct subcellular location is essential for cel