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PMID:8467790
| Citation |
Dube, P, Tavares, P, Lurz, R and van Heel, M (1993) The portal protein of bacteriophage SPP1: a DNA pump with 13-fold symmetry. EMBO J. 12:1303-9 |
|---|---|
| Abstract |
Electron microscopy in combination with image processing is a powerful method for obtaining structural information on non-crystallized biological macromolecules at the 10-50 A resolution level. The processing of noisy microscopical images requires advanced data processing methodologies in which one must carefully avoid the introduction of any form of bias into the data set. Using a novel multivariate statistical approach to the analysis of symmetry, we studied the structure of the bacteriophage SPP1 portal protein oligomer. This portal structure, ubiquitous in icosahedral bacteriophages which package dsDNA, is located at the site of symmetry mismatch between a 5-fold vertex of the icosahedral shell and the 6-fold symmetric (helical) tail. From previous studies such 'head-to-tail connector' structures were generally accepted to be homododecamers assembled in a 12-fold symmetric ring around a central channel. Using a new analysis methodology we have found that the phage SPP1 portal structure exhibits 13-fold cyclical symmetry: a new point group organization for oligomeric proteins. A model for the DNA packaging mechanism by 13-fold symmetric portal protein assemblies is presented which attributes a coherent functional meaning to their unusual symmetry. |
| Links | |
| Keywords |
Biological Transport; Capsid/ultrastructure; Coliphages/ultrastructure; DNA, Viral/metabolism; Image Processing, Computer-Assisted; Macromolecular Substances; Microscopy, Electron/methods; Viral Proteins/ultrastructure |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0046798: viral portal complex |
ECO:0000314: |
C |
"In this model one full 3600 rotation of the portal protein corresponds to inserting 65 bp of dsDNA at the expense of a minimum of 32.5 ATPs, if it is assumed that each equivalent unitary interaction between the two structures is coupled to one ATP hydrolysis reaction and leads to the translocation of 2 bp (Figure 3d-e). Furthermore, the model predicts (Figure 4) that the portal protein subunits are activated in the order: 1, 4, 7, 10, 13, 3, 6, 9, 12, 2, 5, 8, 11, 1, etc., thereby equally employing all subunits of the portal structure during the translocation process." |
complete | ||||
Notes
See also
References
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