User:Tom Gluick/glutamine synthetase/Assignment 8
From Proteopedia
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Assignment: My Intent
Assignment 8: IIIB: Central-loop: Map the interactions involving the central loop that stabilize quaternary structure. Explain how these interactions contribute to quaternary structure stability.[1][2]
My hope and intent: I hoped the students would map the interactions the central loop makes with other components in Glutamine synthetase using the information in PDBsum as a guide. Comments upon how the the various interactions lead to stabilizing the complex would be left to their imaginations.
Student Contribution
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Glutamine synthetase is composed of twelve subunits, formed as two hexameric rings. The two rings are held together by twelve central loops which extend into the central region of the complex and include a small, four stranded β loop . Each loop is 33 residues long and has a convex shape. The spatial orientation of the loops has been found to be less accessible for interactions to occur, contributing to the catalytic activity of the enzyme.
The central loop (residues 156-188) is a site where covalent modifications, with inhibitory effects are found. This segment of the complex is subject to proteolysis by four secreted proteases, which cleave specific residues. Another covalent modification known to occur at central loop of Glutamine synthetase is ADP-ribosylation of Arg-172 .
It is evident then that the central loop of glutamine synthetase (residues 156-188) is an important component of the enzyme, anchoring the subunits together and providing the spatial orientation necessary for activity. Therefore the central loop contributes both to the function and stabilization, via numerous hydrophobic interactions and four different hydrogen bonding interactions of the quartenary structure of Glutamine synthetase.
References:
1. Fisher, M. T., Stadtman, E. R., Oxidative Modification of Escherichia coli Glutamine Synthetase, The Journal of Biological Chemistry, 1992, Vol 267. No3, 1872-1880
2. Moss, J., Stanley, S., Levine, R. L., Inactivation of Bacterial Glutamine Synthetase by ADP-ribosylation, The Journal of Biological Chemistry, 1990, Vol. 265, No. 34, 21056-21060
3. Yamashita, M. M., Almassy, R. J., Janson, C. A., Cascio, D., Eisenberg, D., Refined Atomic Model of Glutamine Synthetase at 3.5 A Resolution, The Journal of Biochemistry, 1989, Vol. 264, No. 30, 17681-17690
Authors
Kary Atkinson
Murteza Shahkolahi
Annette Zeender
Assessment
These students had some difficulty with the WIKI script as the green links contain the default language. I do remember when meeting with other groups that other students had some intitial difficulty with the syntax of the script. I feel there is enough information available for students to write the script properly.
The presentation had strong points and weak points.
The presentation does show that some fabulous visuals can be made when students exercise their imagination while working with SAT.
On the otherhand, some visuals fail to emphasize the text effectively; for instance see the last green link.
