A Comparison of DNA Packaging in the Virions of fd, Xf, and Pf1

Abstract

In this article comparisons are made among structural parameters derived from physicochemical data for fd, Pf1, and Xf viruses and, in some cases, those for the filamentous complex formed between fd DNA and the fd gene-V protein. Each of these nucleoproteins contains a circular, single-stranded (SS) DNA molecule and each is about 10⁴ Å in length and 10² Å in diameter. In spite of these common characteristics, their structures differ significantly.

Viruses and Hosts
All known filamentous bacterial viruses have gram-negative bacteria as hosts. Those infecting strains of Escherichia coli carrying the F⁺ transmissible sex factor include f1, fd, M13, ZJ/2, Ec9, AE2, and δ A (see Marvin and Hohn 1969). Because no structural differences have yet been reported for these viruses, we can assume that the structural parameters of fd hold for all of them. According to a number of criteria, two other viruses of E. coli, If1 (Meynell and Lawn 1968) and Ike (Khatoon et al. 1972), have structures that are similar to that of fd, even though their host specificities are determined by different transmissible genetic factors (Lawn et al. 1967; Khatoon and Iyer 1971). Members of a second group of viruses have Pseudomonas aeruginosa strains as hosts. These are Pf1, Pf2 (Takeya and Amako 1966; Minamishima et al. 1968), and Pf3 (Stanisich 1974), but structural data are available only for Pf1. The third virus in our comparison is Xf, the only filamentous virus of Xanthomonas oryzae that has been described (Kuo et al. 1967). One filamentous...