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Susquehanna Valley Local Section

March 2007 Meeting

Reception: at 6:00 p.m. in the Apple Community Room in Susquehanna University's Garrett Sports Complex. (Once you enter the Garrett Sports complex, the Apple Community Room is the 5^th entrance on the left.)
Dinner: will be buffet-style with a selection of carved roast beef, chicken in wine sauce, roasted red potatoes, a vegetable, assorted desserts and a beverage. The cost will be $15 - $20 per person. Those interested in attending the dinner please contact Geneive Henry at 570-372-4222 on or before Friday, 9 March 2007.
Meeting: at 7:45 p.m. in Fisher Hall Room 321

Directions: see below

Taking a Hit for the Team: Self-Sacrifice as an Enzymatic Strategy in the Biosynthesis of Lipoic Acid
Lipoic acid is an eight-carbon straight-chain fatty acid containing sulfur atoms at carbons 6 and 8. In addition to its antioxidant properties, its most notable function is as a key cofactor that is employed by several multienzyme complexes that are involved in energy metabolism (pyruvate dehydrogenase and -ketoglutarate dehydrogenase complexes), or the catabolism of glycineα (glycine cleavage system), branch-chain amino acids (branch-chain amino acid dehydrogenase complex), and acetoin (acetoin dehydogenase complex). In its role as a cofactor, it must be attached covalently in an amide linkage to the epsilon nitrogen of a specific lysine residue on a lipoyl carrying protein of the complex. This important post-translational modification can be achieved via two different mechanisms: one in which exogenous intact lipoic acid is activated and then appended to a lipoyl carrying protein, and one in which lipoic acid is constructed de novo in its cofactor form onto a lipoyl carrying protein.

This lecture will describe the characterization of lipoyl synthase, which catalyzes the terminal step in the de novo pathway for the biosynthesis of the lipoyl cofactor, which is the insertion of sulfur atoms at carbons 6 and 8 of an n-octanoyl chain that is covalently bound to lipoyl carrying proteins. Lipoyl synthase is a member of the radical-SAM superfamily of enzymes, wherein S-adenosylmethionine is used to generate a 5′-deoxyadenosyl 5′-radical, which is a required intermediate in catalysis. A working hypothesis for the role of the 5′-deoxyadenosyl 5′-radical will be presented, as will experiments that have been conducted to test that working hypothesis. Interestingly, data will be presented that indicate that the protein is both a catalyst and a substrate.

Dr. Squire J. Booker earned his BA in Chemistry from Austin College in Sherman, Texas and Ph.D. in Biochemistry from MIT. After postdoctoral fellowships at Université René Descartes in Paris, France and University of Wisconsin⁄Madison, Dr. Booker joined the Penn State University faculty where he is currently Associate Professor of Biochemistry and Molecular Biology.

Directions to Susquehanna University
From Route 80 West: Take the Danville exit, 224. Take Route 54 East to Route 11 South towards Selinsgrove. Continue left on Route 11/15 South.
From Route 80 East: Take the Lewisburg exit, 210A. Take Route 15 South towards Selinsgrove. Turn right onto Route 11/15 South.

Route 11/15 South becomes Market Street. Turn right onto W. Pine Street (just beyond BJ′s). West Pine Street becomes University Avenue. Follow the campus map to visitor parking. The campus map can be found at http://www.susqu.edu/admissions/maps.htm