资源环境科技发展态势分析平台

The structure of thyroglobulin, the enormous protein that acts as a precursor for thyroid hormones, has been determined, and its hormone-forming tyrosine amino-acid residues have been identified.

Fresh insight into the biosynthesis of thyroid hormones.

The beta(1)-adrenoceptor (beta(1)AR) is a G-protein-coupled receptor (GPCR) that couples(1)to the heterotrimeric G protein G(s). G-protein-mediated signalling is terminated by phosphorylation of the C terminus of the receptor by GPCR kinases (GRKs) and by coupling of beta-arrestin 1 (beta arr1, also known as arrestin 2), which displaces G(s)and induces signalling through the MAP kinase pathway(2). The ability of synthetic agonists to induce signalling preferentially through either G proteins or arrestins-known as biased agonism(3)-is important in drug development, because the therapeutic effect may arise from only one signalling cascade, whereas the other pathway may mediate undesirable side effects(4). To understand the molecular basis for arrestin coupling, here we determined the cryo-electron microscopy structure of the beta(1)AR-beta arr1 complex in lipid nanodiscs bound to the biased agonist formoterol(5), and the crystal structure of formoterol-bound beta(1)AR coupled to the G-protein-mimetic nanobody(6)Nb80. beta arr1 couples to beta(1)AR in a manner distinct to that(7)of G(s)coupling to beta(2)AR-the finger loop of beta arr1 occupies a narrower cleft on the intracellular surface, and is closer to transmembrane helix H7 of the receptor when compared with the C-terminal alpha 5 helix of G(s). The conformation of the finger loop in beta arr1 is different from that adopted by the finger loop of visual arrestin when it couples to rhodopsin(8). beta(1)AR coupled to beta arr1 shows considerable differences in structure compared with beta(1)AR coupled to Nb80, including an inward movement of extracellular loop 3 and the cytoplasmic ends of H5 and H6. We observe weakened interactions between formoterol and two serine residues in H5 at the orthosteric binding site of beta(1)AR, and find that formoterol has a lower affinity for the beta(1)AR-beta arr1 complex than for the beta(1)AR-G(s)complex. The structural differences between these complexes of beta(1)AR provide a foundation for the design of small molecules that could bias signalling in the beta-adrenoceptors.

A cryo-electron microscopy structure of the beta 1-adrenoceptor coupled to beta-arrestin 1 and activated by the biased agonist formoterol, as well as the crystal structure of a related formoterol-bound adrenoreceptor, provide insights into biased signalling in these systems.

The structure of human diacylglycerol O-acyltransferase 1, a membrane protein that synthesizes triacylglycerides, is solved with cryo-electron microscopy, providing insight into its function and mechanism of enzymatic activity.

Diacylglycerol O-acyltransferase 1 (DGAT1) synthesizes triacylglycerides and is required for dietary fat absorption and fat storage in humans(1). DGAT1 belongs to the membrane-bound O-acyltransferase (MBOAT) superfamily, members of which are found in all kingdoms of life and are involved in the acylation of lipids and proteins(2,3). How human DGAT1 and other mammalian members of the MBOAT family recognize their substrates and catalyse their reactions is unknown. The absence of three-dimensional structures also hampers rational targeting of DGAT1 for therapeutic purposes. Here we present the cryo-electron microscopy structure of human DGAT1 in complex with an oleoyl-CoA substrate. Each DGAT1 protomer has nine transmembrane helices, eight of which form a conserved structural fold that we name the MBOAT fold. The MBOAT fold in DGAT1 forms a hollow chamber in the membrane that encloses highly conserved catalytic residues. The chamber has separate entrances for each of the two substrates, fatty acyl-CoA and diacylglycerol. DGAT1 can exist as either a homodimer or a homotetramer and the two forms have similar enzymatic activity. The N terminus of DGAT1 interacts with the neighbouring protomer and these interactions are required for enzymatic activity.

The X-ray crystal structure of the potassium channel TASK-1 reveals the presence of an X-gate, which traps small-molecule inhibitors in the intramembrane vestibule and explains their low washout rates from the channel.

A new and highly pathogenic coronavirus (severe acute respiratory syndrome coronavirus-2, SARS-CoV-2) caused an outbreak in Wuhan city, Hubei province, China, starting from December 2019 that quickly spread nationwide and to other countries around the world(1-3). Here, to better understand the initial step of infection at an atomic level, we determined the crystal structure of the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 bound to the cell receptor ACE2. The overall ACE2-binding mode of the SARS-CoV-2 RBD is nearly identical to that of the SARS-CoV RBD, which also uses ACE2 as the cell receptor(4). Structural analysis identified residues in the SARS-CoV-2 RBD that are essential for ACE2 binding, the majority of which either are highly conserved or share similar side chain properties with those in the SARS-CoV RBD. Such similarity in structure and sequence strongly indicate convergent evolution between the SARS-CoV-2 and SARS-CoV RBDs for improved binding to ACE2, although SARS-CoV-2 does not cluster within SARS and SARS-related coronaviruses(1-3,5). The epitopes of two SARS-CoV antibodies that target the RBD are also analysed for binding to the SARS-CoV-2 RBD, providing insights into the future identification of cross-reactive antibodies.