title: Assembly of bacteriophage lambda terminase into a viral DNA maturation and packaging machine.
abstract: Terminase enzymes are common to complex double-stranded DNA viruses and function to package viral DNA into the capsid. We recently demonstrated that the bacteriophage lambda terminase gpA and gpNu1 proteins assemble into a stable heterotrimer with a molar ratio gpA1/gpNu1(2). This terminase protomer possesses DNA maturation and packaging activities that are dependent on the E. coli integration host factor protein (IHF). Here, we show that the protomer further assembles into a homogeneous tetramer of protomers of composition (gpA1/gpNu1(2))4. Electron microscopy shows that the tetramer forms a ring structure large enough to encircle duplex DNA. In contrast to the heterotrimer, the ring tetramer can mature and package viral DNA in the absence of IHF. We propose that IHF induced bending of viral DNA facilitates the assembly of four terminase protomers into a ring tetramer that represents the catalytically competent DNA maturation and packaging complex in vivo. This work provides, for the first time, insight into the functional assembly state of a viral DNA packaging motor.
authors.affiliation: Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, 4200 East Ninth Avenue C238, Denver, Colorado 80262, USA.
authors.forename: Nasib Karl
authors.initials: NK
authors.lastname: Maluf
authors.forename: Hélène
authors.initials: H
authors.lastname: Gaussier
authors.forename: Elke
authors.initials: E
authors.lastname: Bogner
authors.forename: Michael
authors.initials: M
authors.lastname: Feiss
authors.forename: Carlos Enrique
authors.initials: CE
authors.lastname: Catalano
mesh_terms: D010582:Bacteriophage lambda / Q000201:enzymology* / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D002384:Catalysis; D004261:DNA Replication / Q000235:genetics*; D004279:DNA, Viral / Q000096:biosynthesis* / Q000737:chemistry / Q000648:ultrastructure; D004706:Endodeoxyribonucleases / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D008970:Molecular Weight; D011401:Promoter Regions, Genetic; D014461:Ultracentrifugation; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D004279:DNA, Viral; D020409:Molecular Motor Proteins; D004706:Endodeoxyribonucleases; C030894:terminase