The many components of cells are separated by membrane bound compartments such as periplasm, inner membrane and cytoplasm. Molecules may cross these membranes by simple or facilitated diffusion; however, active transport with ATP is required to drive the transport of large, highly charged and highly hydrophobic molecules against their concentration gradient. This energy requiring process couples ATP hydrolysis with transport proteins to bypass the impermeable nature of membranes (Wikipedia, Nov. 14, 2005, electronic communication). In this paper, we will explore and demonstrate how transport proteins achieve active transport through protein conformation changes and protein phosporylation .
Transport protein forms on transmembrane or membrane-crossing domains (TMD) that span the membrane successively as α-helices (see Fig 1) (Higgins, 2001). For each domain, there is a hydrophilic and peripherally associated ATP or nucleotide binding domain (NBD) (see Fig 2) (Higgins, 2001).......
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