Sandbox108
From Proteopedia
Glutamine synthetase assignment by UMBC undergraduate students
Glutamine synthetase of Salmonella typhimurium
Tertiary structure of protein is characterized by the “global” folding of a polypeptide chain [1] and mostly affected by () interaction and hydrogen bonding. In general, hydrophobic interaction is a major driving force determining the most tertiary structure of the proteins. Hydrogen bonding is crucial in stabilizing the tertiary structure as well.[2] Also, disulfide bonds stabilize the tertiary structure in residues such as cysteine residues.[3] However, for Salmonella typhimurium it is mostly influenced by the helix-helix interactions between 12-subunits enzymes within two layers.[4]
Glutamine synthetase from Salmonella typhimurium is the 12-subunits enzyme, and has 23 helix-helix interactions involving helices of chain A with four different types of interactions. [5] The 12-subunits enzyme are arranged in two layers of six, such as which is the one of the protein residues of Salmonella typhimurium; at the interface of pairs of subunits within each layer, six anti-parallel beta strands formed cylindrical active sites.[6] Each active site holds two ions surrounded by some [7] Also, the protein ligands to Mn2+ 469 are , , and ; those to Mn2+ 470 are , , and .[8] Glutamine from Salmonella typhimurium has 12-subunits of each of them in pairs within two layers. C-terminus end of the polypetide and a helical thong, which inserts into a pocket formed by two neighboring subunits on the opposite ring, hold the two layers of subunits tightly.[9] Also, can affect the form of tertiary structure, but interactions will contribute to the stability of the intersubunit between two layers more efficiently.[10] In the other hand, the most effective interaction in glutamine synthetase from Salmonella typhimurium is the helix-helix interactions. The folding of the proteins can be affected by the 12-subunits in the residues. In the case of Salmonella typhimurium the helices of chain A has , while most glutamine has uncharged side chain which formed by replacing the hydroxyl of glutamic acid with an amine functional group. Moreover, glutamine from Salmonella typhimurium has two domains; "beta-grasp domain" and "catalytic domain."[11][12] In short, this is N-terminal and C-terminal domain.[13] The N-terminal domain refers to the end of a polypeptide which has a free amine group,[14] and the C-terminal end of the polypeptide has a free carboxyl group.[15] As a result, glutamine synthetase for Salmonella typhimurium depends mostly on the helix-helix interactions involving helices with four different types of interactions. 12-subunits enzymes are arranged in two layers of six, where the hydrogen-bonded beta sheet and hydrophobic interactions occur.
