Marvik O J, Jacobsen E, Dokland T, Lindqvist B H
Institute of Biology, University of Oslo, Blindern, Norway.
Virology. 1994 Nov 15;205(1):51-65. doi: 10.1006/viro.1994.1619.
Several of the structural proteins of phage P2 and its satellite P4 undergo proteolytic processing during development of mature phage particles. Here, we report that uncleaved shell protein, gpN, is present in immature capsids of both P2 and P4, showing that assembly precedes processing. This excludes the possibility that processing of gpN is involved in capsid size determination. We also find that N*, the fully processed version of gpN, produced from a plasmid, can assemble into both P2- and P4-sized particles, implying that the amino-terminal end of gpN is not required for assembly initiation nor for the formation of a T = 4 shell. As may be expected for a scaffolding protein, we find that gpO coexists with gpN in immature P2, as well as P4, capsids. This result supports the conclusion that gpO is required for both phages and strongly suggests that the O derivative, h7 (found in mature capsids), results from proteolytic cleavage after gpN/gpO coassembly.
噬菌体P2及其卫星噬菌体P4的几种结构蛋白在成熟噬菌体颗粒的发育过程中会经历蛋白水解加工。在此，我们报告未切割的外壳蛋白gpN存在于P2和P4的未成熟衣壳中，这表明组装先于加工。这排除了gpN的加工参与衣壳大小确定的可能性。我们还发现，由质粒产生的gpN的完全加工形式N*可以组装成P2和P4大小的颗粒，这意味着gpN的氨基末端对于组装起始和T = 4外壳的形成都不是必需的。正如对支架蛋白所预期的那样，我们发现gpO与gpN共存于未成熟的P2以及P4衣壳中。这一结果支持了gpO对两种噬菌体都是必需的这一结论，并强烈表明在gpN/gpO共组装后，O衍生物h7（存在于成熟衣壳中）是蛋白水解切割的结果。
