International Cooperation

Major Advancement Made on Research of Glucagon Receptor

The research results on the seven transmembrane helical domain of human GCGR at 3.4 ? resolution, complemented by extensive site-specific mutagenesis, and a hybrid model of glucagon bound to GCGR to understand the molecular recognition of the receptor for its native ligand, which were obtained by the joint efforts of scientists from China, the USA, Netherlands and Danmark, etc, including the Scripps Institute, the National Center for Drug Scereening and the CAS Key Lab of Receptor Research, Institute of Materia Medica, etc. were reported on line by Nature on July 18? [(2013) doi:10.1038/nature12393]. Their progress in this field was abstracted by the magazine as following: Binding of the glucagon peptide to the glucagon receptor (GCGR) triggers the release of glucose from the liver during fasting; thus GCGR plays an important role in glucose homeostasis. Here we report the crystal structure of the seven transmembrane helical domain of human GCGR at 3.4 ? resolution, complemented by extensive site-specific mutagenesis, and a hybrid model of glucagon bound to GCGR to understand the molecular recognition of the receptor for its native ligand. Beyond the shared seven transmembrane fold, the GCGR transmembrane domain deviates from class A G-protein-coupled receptors with a large ligand-binding pocket and the first transmembrane helix having a ‘stalk’ region that extends three alpha-helical turns above the plane of the membrane. The stalk positions the extracellular domain (~12 kilodaltons) relative to the membrane to form the glucagon-binding site that captures the peptide and facilitates the insertion of glucagon’s amino terminus into the seven transmembrane domain.

The Oldest Known Primate Skeleton Found

A research team led by Dr. Ni Xijun, a research professor from the Institute of Vertebrate Paleontology and Paleoanthropology, CAS, announced a discovery of the oldest known primate skeleton in a paper published in the June 6th issue of Nature. The fossil, named Archicebusachilles, was discovered from the 55 million years old lacustrine depositions near the Jingzhou City of Hubei Province, China. The discovery provided a key evidence for determining the divergent time between anthropoids and other primates, and for understanding the pattern of primate early evolution. It sets a milestone in the paleoprimatology and paleoanthropology research. In the era of Archicebusachilles, the earth was in the so-called Eocene greenhouse period. The climate was warm and humid. Lush forests covered the North and South Poles. Palm trees were even distributed to the Alaska of nowadays. It is a miracle that the primate skeleton could be preserved in so complete condition in this kind of environment. The team led by Ni Xijun includes Dr. Christopher K. Beard from the Carnegie Museum of Nature History, Prof. Daniel L. Gebo from the Northern Illinois University, Prof. Marian Dagosto from the Northwestern University, Drs. Jin Meng and John J. Flynn from the American Museum of Natural History, and Dr. Paul Tafforeau from the European Synchrotron Radiation Facility. The skeleton of Archicebusachilles is 7 million years older than the Darwinius skeleton discovered from the Messel in Germany and Notharctus skeleton discovered in Wyoming in the United States. And furthermore, Archicebusachillesand our human beings belong to the same clade in the phylogenetic tree, whereas Notharctus and Darwinius belong to another clade. They are closer to extant lemurs than to humans. Study on Archicebusachilles has revealed a relatively complete picture that shows the moment when anthropoids just began to separate from other primates. As Ni Xijun said, it is “a great leap for reconstructing the early evolution history of humans and other primates”. The ecological reconstruction shows that Archicebusachilles was a kind of tiny but agile primates. They were active during daytime and capable of leaping, and used eyesight and hands to catch insects.