Observations concerning the sequence of two additional specifically encapsidated RNA fragments originating from the tobacco-mosaic-virus coat-protein cistron.

The incubation of 25-S tobacco mosaic virus (TMV) protein with a mixture of RNA fragments produced by partial T1 RNase digestion of TMV RNA results in the encapsidation of only a few species of RNA. In addition to the most predominant species, fragment 1, whose sequence has been described in the prededing paper, two other species, fragment 41 and fragment 21 are coated by the protein. These two RNA fragments were purified by polyacrylamide gel electrophoresis and subjected to total digestion with pancreatic and T1 RNase. The oligonucleotides were separated by paper electrophoresis and characterized insofar as possible by digestion with the complementary ribonuclease. From the amino acid coding capacity of the oligonucleotides liberated from fragments 41 and 21 by T1 RNase digestion, it appears that these two fragments, like fragment 1, are derived from the coat protein cistron. They are situated immediately prior to fragment 1 and, together with this fragment, consitute a continuous stretch of 232 nucleotides of the cistron which codes for animo acids 53 to 130 of the coat protein. The order of the fragments in the sequence is 21-41-1. A possible model for the secondary structure of this portion of the sequence is proposed.