Ribulose-1,5-bisphosphate carboxylase contains 2992 hydrogen bonds, which force the 16 protein chains to assume 208 helices, 248 beta-strands and 456 turns . Just in case the pattern shown here is somewhat confusing, the structural elements of this enzyme will be demonstrated using a single subunit each .
The small subunit is made up of 123 amino acids. The protein contains a four-stranded antiparallel sheet , which is flanked by two helices. Some turns stabilize the loops. The large subunit contains 475 amino acids (amino acids 1-8 and 464-475 are not visible in the X-ray determined structure). Two domains are to be descerned in the protein. The N-terminal domain figures the first 150 amino acids . This domain contains a four-stranded antiparallel sheet as well as some helices and turns. The carboxy terminal domain is the catalytically important part of the molecule. It's structure is an eight-stranded alpha/beta barrel. The barrel arises from the alternating order of beta-strands and helices . The bottom of the barrel is closed by a helix . The opposite side of the barrel features the active site of the enzyme. Amino acids in the loops between the helices and strands making up the barrel coordinate a megnesium ion . To the other side of the magnesium ion the substrate is bound . In the complete enzyme complex the active site is situated in the interface of two adjacent large subunits . In a spacefilling view of the protein the accessibility of the active center for the substrate is visible within the interface region (if you use the mouse to rotate the protein, you may get the channels straight to focus). Literature: I Andersson, J. Mol. Biol. 259 (1996) 160-174 9-98 © R Bergmann If you don't see a molecular model:http://www.biologie.uni-hamburg.de/lehre/bza/1rxo/e1rxom.htm
The large subunit contains 475 amino acids (amino acids 1-8 and 464-475 are not visible in the X-ray determined structure). Two domains are to be descerned in the protein. The N-terminal domain figures the first 150 amino acids . This domain contains a four-stranded antiparallel sheet as well as some helices and turns.
The carboxy terminal domain is the catalytically important part of the molecule. It's structure is an eight-stranded alpha/beta barrel. The barrel arises from the alternating order of beta-strands and helices . The bottom of the barrel is closed by a helix . The opposite side of the barrel features the active site of the enzyme. Amino acids in the loops between the helices and strands making up the barrel coordinate a megnesium ion . To the other side of the magnesium ion the substrate is bound . In the complete enzyme complex the active site is situated in the interface of two adjacent large subunits . In a spacefilling view of the protein the accessibility of the active center for the substrate is visible within the interface region (if you use the mouse to rotate the protein, you may get the channels straight to focus). Literature: I Andersson, J. Mol. Biol. 259 (1996) 160-174 9-98 © R Bergmann If you don't see a molecular model:http://www.biologie.uni-hamburg.de/lehre/bza/1rxo/e1rxom.htm
In the complete enzyme complex the active site is situated in the interface of two adjacent large subunits . In a spacefilling view of the protein the accessibility of the active center for the substrate is visible within the interface region (if you use the mouse to rotate the protein, you may get the channels straight to focus).
Literature: I Andersson, J. Mol. Biol. 259 (1996) 160-174
