Abstract
ATP-binding cassette transporters perform energy-dependent transmembrane solute trafficking in all organisms. These proteins often mediate cellular resistance to therapeutic drugs and are involved in a range of human genetic diseases. Enzymological studies have implicated a helical subdomain within the ATP-binding cassette nucleotide-binding domain in coupling ATP hydrolysis to solute transport in the transmembrane domains. Consistent with this, structural and computational analyses have indicated that the helical subdomain undergoes nucleotide-dependent movement relative to the core of the nucleotide-binding domain fold. Here we use theoretical methods to examine the allosteric nucleotide dependence of helical subdomain transitions to further elucidate its role in interactions between the transmembrane and nucleotide-binding domains. Unrestrained 30-ns molecular dynamics simulations of the ATP-bound, ADP-bound, and apo states of the MJ0796 monomer support the idea that interaction of a conserved glutamine residue with the catalytic metal mediates the rotation of the helical subdomain in response to nucleotide binding and hydrolysis. Simulations of the nucleotide-binding domain dimer revealed that ATP hydrolysis induces a large transition of one helical subdomain, resulting in an asymmetric conformation of the dimer not observed previously. A coarse-grained elastic network analysis supports this finding, revealing the existence of corresponding dynamic modes intrinsic to the contact topology of the protein. The implications of these findings for the coupling of ATP hydrolysis to conformational changes in the transmembrane domains required for solute transport are discussed in light of recent whole transporter structures.
Highlights
ATP-binding cassette (ABC)3 transporters couple hydrolysis of ATP to vectorial translocation of substrates across cellular membranes, typically against a concentration gradient
Most prokaryotic ABC transporters are importers with the core transmembrane domains (TMDs) and nucleotide-binding domains (NBDs) expressed as separate subunits, whereas most eukaryotic ABC transporters are exporters that commonly have a single polypeptide for the core structure, with each NBD C-terminal to each TMD
Dimerization induces a new cooperative mode, not found in the isolated monomer. This result is consistent with previous biochemical and structural data, which indicate that the dimeric form of the ABC NBD is required for catalytic activity [35,36,37,38,39,40] and illustrates the relationship between the dominant dynamic modes and the functioning of the protein
Summary
ATP-binding cassette (ABC)3 transporters couple hydrolysis of ATP to vectorial translocation of substrates across cellular membranes, typically against a concentration gradient.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have