Crystal structure of a four-layer aggregate of engineered TMV CP implies the importance of terminal residues for oligomer assembly.
BACKGROUND
Crystal structures of the tobacco mosaic virus (TMV) coat protein (CP) in its helical and disk conformations have previously been determined at the atomic level. For the helical structure, interactions of proteins and nucleic acids in the main chains were clearly observed; however, the conformation of residues at the C-terminus was flexible and disordered. For the four-layer aggregate disk structure, interactions of the main chain residues could only be observed through water-mediated hydrogen bonding with protein residues. In this study, the effects of the C-terminal peptides on the interactions of TMV CP were investigated by crystal structure determination.


RESULTS
The crystal structure of a genetically engineered TMV CP was resolved at 3.06 Å. For the genetically engineered TMV CP, a six-histidine (His) tag was introduced at the N-terminus, and the C-terminal residues 155 to 158 were truncated (N-His-TMV CP(19)). Overall, N-His-TMV CP(19) protein self-assembled into the four-layer aggregate form. The conformations of residues Gln36, Thr59, Asp115 and Arg134 were carefully analyzed in the high radius and low radius regions of N-His-TMV CP(19), which were found to be significantly different from those observed previously for the helical and four-layer aggregate forms. In addition, the aggregation of the N-His-TMV CP(19) layers was found to primarily be mediated through direct hydrogen-bonding. Notably, this engineered protein also can package RNA effectively and assemble into an infectious virus particle.


CONCLUSIONS
The terminal sequence of amino acids influences the conformation and interactions of the four-layer aggregate. Direct protein-protein interactions are observed in the major overlap region when residues Gly155 to Thr158 at the C-terminus are truncated. This engineered TMV CP is reassembled by direct protein-protein interaction and maintains the normal function of the four-layer aggregate of TMV CP in the presence of RNA.
State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University, Guiyang, China.
Xiangyang
X
Li
Baoan
B
Song
Xi
X
Chen
Zhenchao
Z
Wang
Mengjiao
M
Zeng
Dandan
D
Yu
Deyu
D
Hu
Zhuo
Z
Chen
Linhong
L
Jin
Song
S
Yang
Caiguang
C
Yang
Baoen
B
Chen
D036022:Capsid Proteins / Q000737:chemistry* / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D015202:Protein Engineering; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D040681:Structural Homology, Protein; D014027:Tobacco Mosaic Virus / Q000737:chemistry* / Q000648:ultrastructure
D036022:Capsid Proteins