[1] Vanderbilt Univ, Nashville, TN 37235 USA
[2] Dartmouth Coll, Hanover, NH 03755 USA
[3] Dept Biochem & Mol Biol, Athens, GA USA
[4] Vanderbilt Univ, Med Ctr, Nashville, TN USA
[5] Washington Univ, St Louis, MO USA
[6] Univ Washington, Seattle, WA 98195 USA