Heterotrimeric G-proteins interact with their G-protein-coupled receptors (GPCRs) via key binding elements comprising the receptor-specific C-terminal segment of the alpha-subunit and the lipid anchors at the alpha-subunit N-terminus and the gamma-subunit C-terminus. Direct information about diffusion and interaction of GPCRs and their G-proteins is mandatory for an understanding of the signal ...

The docking of G␣ to G␤␥ involves extensive contacts: *Department of Medicine binding of the G␣ N-terminal ␣ helix to the side of the Cardiovascular Division G␤ propeller parallel to its central tunnel and binding of Brigham and Women's Hospital the catalytic domain of G␣ to the top surface of the ␤ and Harvard Medical School propeller (see Figure 1). Removal of the N-terminal ␣ Boston, Massach...

During protein synthesis, tRNAs and their associated mRNA codons move sequentially on the ribosome from the A (aminoacyl) site to the P (peptidyl) site to the E (exit) site in a process catalyzed by a universally conserved ribosome-dependent GTPase [elongation factor G (EF-G) in prokaryotes and elongation factor 2 (EF-2) in eukaryotes]. Although the high-resolution structure of EF-G bound to th...

Eukaryotic chromosomes end in short nucleotide repeats that are added by the enzyme telomerase. The catalytic subunit of telomerase has been shown to be most closely related in sequence to reverse transcriptases encoded by eukaryotic retrotransposable elements. This raises the question as to whether the telomerase subunit was present in the first eukaryotes or was derived during early eukaryote...

The two subtypes of mammalian muscle nicotinic acetylcholine receptors (AChR) are generated by the substitution of the 1 (adult) subunit for the g (fetal) subunit within the AChR pentamer. Null mutations of the adultAChR 1-subunit gene are themost commoncauseof theAChRdeficiencysyndrome. This is adisorder of neuromuscular transmission characterizedbynon-progressive fatigablemuscleweaknesspresen...

Although G-protein-coupled receptors (GPCRs) have been shown to assemble into functional homo or heteromers, the role of each protomer in G-protein activation is not known. Among the GPCRs, the gamma-aminobutyric acid (GABA) type B receptor (GABA(B)R) is the only one known so far that needs two subunits, GB1 and GB2, to function. The GB1 subunit contains the GABA binding site but is unable to a...

conclusions single dose therapy of mtx has sufficient power and efficacy in the treatment of ectopic pregnancy, however in patients with higher serum level of β-hcg, the successful treatment increases by using double dose method. using double dose also could decrease the necessity of operation, re-administration of mtx, and duration of hospitalization. results results showed that the rate of su...

Elongation factor (EF) G promotes tRNA translocation on the ribosome. We present three-dimensional reconstructions, obtained by cryo-electron microscopy, of EF-G-ribosome complexes before and after translocation. In the pretranslocation state, domain 1 of EF-G interacts with the L7/12 stalk on the 50S subunit, while domain 4 contacts the shoulder of the 30S subunit in the region where protein S...

Previous studies implicated the involvement of a heterotrimeric G protein in red (R) and far-red (FR) light signal transduction, but these studies utilized pharmacological or gain-of-function approaches and, therefore, are indirect tests. Here, we reexamine the role of the single canonical heterotrimeric G protein in R and FR control of hypocotyl growth using a loss-of-function approach. Single...