title: GTP-mediated macromolecular interactions: the common features of different systems.
abstract: G proteins that serve to transduce external signals in membranes share with protein synthesis factors and tubulin structural and functional features that are common to proteins that participate in reversible GTP-mediated macromolecular interactions. These proteins can bind GTP and GDP with high affinity, adopting different structures depending on whether they are complexed with the nucleotide diphosphate or triphosphate. The GTP.protein complex has high affinity for an acceptor macromolecule (or complex of macromolecules) and interacts with it, affecting its activity. These GTP-binding proteins also possess an intrinsic GTPase activity that is generally stimulated by its interaction with the acceptor. The GTPase activity converts the bound GTP to GDP, switching the configuration of the complexed protein to one of low affinity for the acceptor and causing its dissociation. The protein.GDP complex must exchange its GDP for GTP to allow the protein to acquire the high-affinity structure that can cycle back to the acceptor macromolecule. This exchange of guanine nucleotides requires in several instances exchange factors that can regulate the whole process. A detailed comparison of the features of the different systems is made with respect to structural similarities, regulation by protein phosphorylation, ADP ribosylation by bacterial toxins, and requirements for exchange factors. It is also proposed that there is a similar mechanism that involves ATP/ADP-binding proteins.
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000494:Allosteric Regulation; D001427:Bacterial Toxins / Q000378:metabolism; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D010445:Peptide Elongation Factors / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism; D010766:Phosphorylation; D010786:Photoreceptor Cells / Q000201:enzymology; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D015293:Transducin; D014404:Tubulin / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D007473:Ion Channels; D008565:Membrane Proteins; D010445:Peptide Elongation Factors; D010448:Peptide Initiation Factors; D011518:Proto-Oncogene Proteins; D014404:Tubulin; D000246:Adenosine Diphosphate Ribose; D006160:Guanosine Triphosphate; D010738:Type C Phospholipases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000251:Adenosine Triphosphatases; D020963:GTP Phosphohydrolase-Linked Elongation Factors; D019204:GTP-Binding Proteins; D015293:Transducin; D016283:Proto-Oncogene Proteins p21(ras); D000262:Adenylyl Cyclases