The Kolbeinsey Ridge is a segment of the Mid-Atlantic Ridge located to the north of Iceland in the Arctic Ocean. It is bounded to the south by the Tjörnes Fracture Zone, which connects the submarine ridge to the on-shore Northern Volcanic Zone rifting center in eastern Iceland. The volcanic islands Kolbeinsey and Grímsey lie along the Kolbeinsey Ridge.
20-556: In 1992, Robert Huber and Karl Stetter discovered a new species of thermophilic bacteria here and named it A. pyrophilus . This tectonics article is a stub . You can help Misplaced Pages by expanding it . Robert Huber Robert Huber ( German pronunciation: [ˈʁoːbɛʁt ˈhuːbɐ] ; born 20 February 1937) is a German biochemist and Nobel laureate . known for his work crystallizing an intra membrane protein important in photosynthesis and subsequently applying X-ray crystallography to elucidate
40-548: A peptide bond at the carboxy-terminal (C-terminal) end of a protein or peptide . This is in contrast to an aminopeptidases , which cleave peptide bonds at the N-terminus of proteins. Humans, animals, bacteria and plants contain several types of carboxypeptidases that have diverse functions ranging from catabolism to protein maturation. At least two mechanisms have been discussed. Initial studies on carboxypeptidases focused on pancreatic carboxypeptidases A1, A2, and B in
60-568: A director at the Max Planck Institute for Biochemistry where his team developed methods for the crystallography of proteins . In 1988 he received the Nobel Prize for Chemistry jointly with Johann Deisenhofer and Hartmut Michel . The trio were recognized for their work in first crystallizing an intramembrane protein important in photosynthesis in purple bacteria , and subsequently applying X-ray crystallography to elucidate
80-469: Is proline, Xaa is any amino acid on the C-terminus of a peptide) is called " prolyl carboxypeptidase ". Some, but not all, carboxypeptidases are initially produced in an inactive form; this precursor form is referred to as a procarboxypeptidase . In the case of pancreatic carboxypeptidase A, the inactive zymogen form - pro-carboxypeptidase A - is converted to its active form - carboxypeptidase A - by
100-501: The digestion of food. Most carboxypeptidases are not, however, involved in catabolism . Instead they help to mature proteins, for example post-translational modification . They also regulate biological processes, such as the biosynthesis of neuroendocrine peptides such as insulin requires a carboxypeptidase. Carboxypeptidases also function in blood clotting , growth factor production, wound healing , reproduction , and many other processes. Carboxypeptidases hydrolyze peptides at
120-494: The Zn coordinated water by Glu 270 provides an activated hydroxide nucleophile which attacks the amide carbonyl group in the peptide bond in a nucleophilic addition. The negatively charged intermediates that are formed during hydrolysis are stabilized by the Zn ion. The interaction between the carbonyl group and the neighbouring arginine, Arg 217, also stabilizes the negatively charged intermediates. The zinc-bound hydroxide interacts with
140-526: The amide with the electrostatic stabilization of the transition state provided by the Zn ion and the neighbouring arginine. The second proposed mechanism via an anhydride has similar steps but there is a direct attack of Glu270 on the carbonyl group, and then the interaction of Glu270 on the Zn -bound amide forms an anhydride instead which can subsequently be hydrolyzed by water. Carboxypeptidases are usually classified into one of several families based on their active site mechanism. These names do not refer to
160-460: The chemical formula of the important insect hormone edtyson which had eluded the chemists. He then demonstrated that the tertiary fold of the polypeptide chain in the haemoglobin of the fly larva chironomus closely resembled that in Kendrew's sperm whale myoglobin , indicating for the first time that this fold had been preserved throughout evolution. Huber's next achievement was the solution of
180-739: The development of Structural Biology at the university on a part-time basis. Since 2005 he has been doing research at the Center for medical biotechnology of the University of Duisburg-Essen . Huber was one of the original editors of the Encyclopedia of Analytical Chemistry . In 1977 Huber was awarded the Otto Warburg Medal . In 1988 he was awarded the Nobel Prize and in 1992 the Sir Hans Krebs Medal . Huber
200-404: The discovery of the remarkable activation mechanism of this enzyme, and of the complex of thrombin with hirudin , which showed the molecular mechanism of inhibition of blood clotting by this leech toxin. In parallel with this work, Huber solved the structures of several immunoglobulin fragments. He was the first to determine the structure of the complement-activating F-fragment, which was also
220-518: The first amide or polypeptide bond on the C-terminal end of the chain. Carboxypeptidases act by replacing the substrate water with a carbonyl (C=O) group. The carboxypeptidase A hydrolysis reaction has two mechanistic hypotheses, via a nucleophilic water and via an anhydride. In the first proposed mechanism, a promoted-water pathway is favoured as Glu270 deprotonates the nucleophilic water. The Zn ion, along with positively charged residues, decreases
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#1732765308115240-532: The first variable and the first constant domains in Fab-fragments. Huber's structure of citrate synthase revealed a striking example of a conformational change undergone by an enzyme on combination with its substrate by a process of induced fit. Huber shared the Nobel Prize for Chemistry in 1988 with Michel and Deisenhofer for their determination of the remarkable and supremely important structures of
260-421: The pKa of the bound water to approximately 7. Glu 270 has a dual role in this mechanism as it acts as a base to allow for the attack at the amide carbonyl group during nucleophilic addition. It acts as an acid during elimination when the water proton is transferred to the leaving nitrogen group. The oxygen on the amide carbonyl group does not coordinate to the Zn until the addition of the water. The deprotonation of
280-625: The photochemical reaction centre of Rhodopseudomonas viridis and of phycocyanin , the light harvesting protein of the blue-green alga Mastiglocadus laminosus. This protein binds linear tetrapyrroles in a tertiary fold reminiscent of the globins , which brought Huber back full circle to his first structure, erythrocruerin , Huber has also determined the structures of several copper-containing electron-transfer proteins , including that of ascorbate oxidase , and of other metallo-enzymes. These studies have thrown new light on electron-transfer systems and on zinc coordination in proteins. He has also solved
300-620: The protein's structure. He was born on 20 February 1937 in Munich where his father, Sebastian, was a bank cashier. He was educated at the Humanistisches Karls-Gymnasium from 1947 to 1956 and then studied chemistry at the Technische Hochschule , receiving his diploma in 1960. He stayed, and did research into using crystallography to elucidate the structure of organic compounds . In 1971 he became
320-475: The protein's structure. The information provided the first insight into the structural bodies that performed the integral function of photosynthesis. This insight could be translated to understand the more complex analogue of photosynthesis in cyanobacteria which is essentially the same as that in chloroplasts of higher plants. In 2006, he took up a post at the Cardiff University to spearhead
340-424: The selectivity of the amino acid that is cleaved. Another classification system for carboxypeptidases refers to their substrate preference. A metallo-carboxypeptidase that cleaves a C-terminal glutamate from the peptide N -acetyl- L -aspartyl- L -glutamate is called " glutamate carboxypeptidase ". A serine carboxypeptidase that cleaves the C-terminal residue from peptides containing the sequence -Pro-Xaa (Pro
360-420: The structure of trypsin inhibitor and the demonstration that in its complex with trypsin it mimicked the tetrahedral transition state of the enzyme's substrate. Since then he has determined the structures of many other proteinases, their inactive precursors and their inhibitors, and has established himself as the world authority in this field. Outstanding structures are those of procarboxypeptidase , which led to
380-429: The structure of an important class of calcium binding proteins – the annexins. Finally his very accurate structures have provided important insights into the different degrees of mobility within protein molecules. Huber has published some 400 papers. Huber is married and has four children. Carboxypeptidase A carboxypeptidase ( EC number 3.4.16 - 3.4.18) is a protease enzyme that hydrolyzes (cleaves)
400-522: Was elected a member of Pour le Mérite for Sciences and Arts , in 1993 and Foreign Member of the Royal Society (ForMemRS) in 1999 . His certificate of election reads: Huber has built up, led and still leads the most productive protein crystallography laboratory in Europe. His own contributions to crystallography, made over a period of some 25 years, are prodigious. For his PhD thesis he solved
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