From Proteopedia

Revision as of 20:35, 18 December 2008

Uzoma Anele, Sandeep Pulugurtha Undergraduate students at the University of Maryland, Baltimore County.

Helical Thong of Glutamine Synthetase

Helical thongs provide a significant amount of intersubunit stabilization to the quaternary structure of glutamine synthetase by binding together subunits from the two layers. There exist 12 helical thongs in glutamine synthetase, each extending from each subunit. A typical , shown here in red, is composed of a nonpolar carboxyl terminus (in this case of subunit A) that inserts into a created by two adjoining subunits (in this case subunits G and L, shown in yellow and teal, respectively) on the opposite, corresponding layer. An example of the details the C-terminal helix in red and the hydrophobic pocket in blue. Thirty-seven of the 77 residues of which the helical thong and hydrophobic pocket consist, are (shown in gray) and are involved in the direct contact between the helical thong and pocket. Approximations of the stabilizing free eneregy created by these hydrophobic interactions suggest that helical thongs rely much more on hydrophobic interactions than hydrogen bonds. These residues contain an atypical abundance of , 16% and 10%, respectively (with proline shown in pink and valine in green). This unusual amount may serve to enhance its rigidity and cohesion. The helical thong complex can be seen in relation to the with the helical thong of the A subunit shown in blue, and the hydropobic pockets created by the G and L subunits shown in yellow and teal, respectively. ^{[1] [2]}

References

1. Eisenberg, D., et.al., Structure-function relationships of glutamine synthetases, Biochim Biophys Acta 2000: 1477, 122-145.

2. Yamashita, M. M., et.al., Refined Atolnic Model of Glutamine Synthetase at 3.5 A Resolution, J Biol Chem 1989 264: 17681-17690.

1. ↑ Eisenberg, D., et.al., Structure-function relationships of glutamine synthetases, Biochim Biophys Acta 2000: 1477, 122-145.
2. ↑ Yamashita, M. M., et.al., Refined Atolnic Model of Glutamine Synthetase at 3.5 A Resolution, J Biol Chem 1989 264: 17681-17690.