A radiopolyadenylated rabbit globin mRNA was treated with different concentrations of ribonuclease V1 from cobra venom. 2. The enzymatic digests were chromatographed on an aminophenylboronate-agarose column, which specifically captured the cap structure i.e. m7G(5') ppp (5') NmP. 3. When the capture fragment was chromatographed on a Sephadex G-100 column, its size was smaller than the native molecule and also bore radioactivity, i.e. a poly(A) tail. 4. These results provide evidence that the 5' end (which encompasses the cap structure) of rabbit globin mRNA is hybridized and in close proximity to its 3' end. 5. We conclude that this conformation is required for messenger translation efficiency.
