GONUTS has been updated to MW1.31 Most things seem to be working but be sure to report problems.
PMID:19109896
| Citation |
Sun, S, Kondabagil, K, Draper, B, Alam, TI, Bowman, VD, Zhang, Z, Hegde, S, Fokine, A, Rossmann, MG and Rao, VB (2008) The structure of the phage T4 DNA packaging motor suggests a mechanism dependent on electrostatic forces. Cell 135:1251-62 |
|---|---|
| Abstract |
Viral genomes are packaged into "procapsids" by powerful molecular motors. We report the crystal structure of the DNA packaging motor protein, gene product 17 (gp17), in bacteriophage T4. The structure consists of an N-terminal ATPase domain, which provides energy for compacting DNA, and a C-terminal nuclease domain, which terminates packaging. We show that another function of the C-terminal domain is to translocate the genome into the procapsid. The two domains are in close contact in the crystal structure, representing a "tensed state." A cryo-electron microscopy reconstruction of the T4 procapsid complexed with gp17 shows that the packaging motor is a pentamer and that the domains within each monomer are spatially separated, representing a "relaxed state." These structures suggest a mechanism, supported by mutational and other data, in which electrostatic forces drive the DNA packaging by alternating between tensed and relaxed states. Similar mechanisms may occur in other molecular motors. |
| Links |
PubMed Online version:10.1016/j.cell.2008.11.015 |
| Keywords |
Bacteriophage T4/metabolism; Crystallography, X-Ray; DNA Packaging; Models, Molecular; Static Electricity; Viral Proteins/chemistry; Viral Proteins/metabolism; Virus Assembly |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0016887: ATPase activity |
ECO:0000315: |
F |
The ATPase protein was compared to two mutants (W533A and ΔS527G538) which had weakened interactions between their domains. The mutants were then compared to the wild-type with a Packaging ATPase assay. Both of the mutants had a loss of their ATPase activity. This is proven in figure 3e, where the concentration of cold ATP was increased every hour, for the wild-type and mutants. The third phosphate group was only cleaved in only the wild-type samples, which is seen in the appearance of the upper bands in the thin layer chromotherapy. |
complete | ||||
| GO:0098009: virus terminase, large subunit |
ECO:0000314: |
C |
Fig 1 of the paper illustrates gp17 as a large terminase. |
complete | ||||
| GO:0004518: nuclease activity |
ECO:0000314: |
F |
The assay experiment of the gp17 terminase can be viewed in figure 3b. Lane's 0, 1, and 2 are how many hours after the addition of isopropyl β-D-1-thiogalactopyranoside (IPTG). This induces the expression of the DNA samples. The mutant sample are then compared to the known DNA. It is then compared to the mutant types, the mutant types did not have cleaved DNA. Proving its identity as a nuclease. |
complete | ||||
| GO:0004536: deoxyribonuclease activity |
ECO:0000315: |
F |
Figure 3b compares the mutant gp17 proteins to the wild types. Arg406 in T4 participates in binding DNA and nuclease activity. Mutant "Arg406Ala" showed that any substitutions in amino acids at the 406 position produced a null phenotype. Meaning that when they tested the phages in a plating assay the mutants failed to produce plaques. See figure 3b shows that unlike the wild-type, the mutant R406A did not degrade the DNA after 2 hours of incubation. |
complete | ||||
Notes
See also
References
See Help:References for how to manage references in GONUTS.
