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Acta Crystallogr Sect F Struct Biol Cryst Commun. 2013 Mar 1;69(Pt 3):275-9. doi: 10.1107/S174430911300184X. Epub 2013 Feb 22.

Expression, purification, crystallization and preliminary X-ray diffraction analysis of a lactococcal bacteriophage small terminase subunit.

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  • 1Materials Science and Engineering, CSIRO, 343 Royal Parade, Parkville, Victoria 3052, Australia.


Terminases are enzymes that are required for the insertion of a single viral genome into the interior of a viral procapsid by a process referred to as 'encapsulation or packaging'. Many double-stranded DNA viruses such as bacteriophages T3, T4, T7, λ and SPP1, as well as herpes viruses, utilize terminase enzymes for this purpose. All the terminase enzymes described to date require two subunits, a small subunit referred to as TerS and a large subunit referred to as TerL, for in vivo activity. The TerS and TerL subunits interact with each other to form a functional hetero-oligomeric enzyme complex; however the stoichiometry and oligomeric state have not been determined. We have cloned, expressed and purified recombinant small terminase TerS from a 936 lactococcal bacteriophage strain ASCC454, initially isolated from a dairy factory. The terminase was crystallized using a combination of nanolitre sitting drops and vapour diffusion using sodium malonate as the precipitant, and crystallization optimized using standard vapour-diffusion hanging drops set up in the presence of a nitrogen atmosphere. The crystals belong to the P2 space group, with unit-cell parameters a=73.93, b=158.48, c=74.23 Å, and diffract to 2.42 Å resolution using synchrotron radiation. A self-rotation function calculation revealed that the terminase oligomerizes into an octamer in the asymmetric unit, although size-exclusion chromatography suggests that it is possible for it to form an oligomer of up to 13 subunits.


DNA-binding protein; Siphoviridae bacteriophage; small terminase subunit

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