1Department of Immunology, Waiter Reed Army Institute of Research, Washington, D.C. 20307-5100; 2Tropical Disease Unit, Division of Infectious Diseases, The Toronto Hospital and The University of Toronto, Toronto, Ontario, Canada M5G 2C4 In vitro transcription and translation are powerful tools for examining the s t ructure-funct ion relationships of proteins. Genes can be cloned into plasmid v...