Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.|Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.|Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.|Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.|Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.|Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.|Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.