Purification of the Elongation Factors Present in Spinach Chloroplasts

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Abstract
Elongation factor G (EF-Gchl) and elongation factor Tu (EF-Tuchl) were purified from isolated spinach chloroplasts. On polyacrylamide gel electrophoresis the purified proteins appeared to be at least 70% pure. The MW was estimated to be 77,000 and 45,500 for EF -Gchl and EF-Tuchl respectively. Chloroplast elongation factor T (EF-Tchl) was only partially purified. Gel electrophoresis under non-denaturing and denaturing conditions indicated that EF-Tchl is most probably composed of 2 polypeptides, one of which has an electrophoretic mobility identical to that of EF-Tuchl. EF-Tuchl appeared to represent approximately 7% of the chloroplast soluble protein while EF-Gchl accounted for less than 1%. As in the case of the bacterial factors, EF-Tuchl, it was assumed that the 3 elongation factors represented approximately 10% of the chloroplast soluble protein.