Ras Protein and Pancreas Cancer: Difference between revisions

Proteins are structured with alpha helices and beta sheets, in this case Ras proteins are made up of five alpha helices and 6 beta sheets. The diphosphate-binding loop G1 (also known as P-loop), with the consensus sequence, connects the β1 strand to the α1 helix and contacts the α- and βphosphates of the guanine nucleotide. The connection between the α1 helix and the β2 strand corresponds to G2 and contains a conserved <scene name='81/814069/Thrmg/1'>threonine residue</scene> (Thr35) involved in Mg2+coordination. The G3 domain, at the NH2 terminus of the α2 helix, links the sites for binding Mg2+ and the γ-phosphate of GTP. The G4 domain that links the β5 strand and the α4 helix recognizes the guanine ring. The G5 loop, located between β6 and helix α5, reinforces the guanine base recognition site <ref name='Gervaise'>doi:10.1002/bip.22840</ref>. Ras proteins act as connectors which connect the interior of the cell with the cell surface <ref name='Gervaise'>doi:10.1002/bip.22840</ref>. The binding to GTP and GDP determines whether they are activated or not, they undergo a conserved mechanism: Ras functions require the participation of distinct regulatory proteins to control the GDP/GTP cycling rate <ref name='Gervaise'>doi:10.1002/bip.22840</ref>. Indeed, the extent and duration of Ras activation in cells depends on the interplay between a variety of negative and positive regulators of the Ras cycle <ref name='Gervaise'>doi:10.1002/bip.22840</ref>.