Thermodynamic Interrogation of the Assembly of a Viral Genome Packaging Motor Complex
Teng-Chieh Yang, David Ortiz, Lyn’Al Nosaka, Gabriel C. Lander, Carlos Enrique Catalano
Abstract
Viral terminase enzymes serve as genome packaging motors in many complex double-stranded DNA viruses. The functional motors are multiprotein complexes that translocate viral DNA into a capsid shell, powered by a packaging ATPase, and are among the most powerful molecular motors in nature. Given their essential role in virus development, the structure and function of these biological motors is of considerable interest. Bacteriophage λ-terminase, which serves as a prototypical genome packaging motor, is composed of one large catalytic subunit tightly associated with two DNA recognition subunits. This protomer assembles into a functional higher-order complex that excises a unit length genome from a concatemeric DNA precursor (genome maturation) and concomitantly translocates the duplex into a preformed procapsid shell (genome packaging). While the enzymology of λ-terminase has been well described, the nature of the catalytically competent nucleoprotein intermediates, and the mechanism describing their assembly and activation, is less clear. Here we utilize analytical ultracentrifugation to determine the thermodynamic parameters describing motor assembly and define a minimal thermodynamic linkage model that describes the effects of salt on protomer assembly into a tetrameric complex. Negative stain electron microscopy images reveal a symmetric ring-like complex with a compact stem and four extended arms that exhibit a range of conformational states. Finally, kinetic studies demonstrate that assembly of the ring tetramer is directly linked to activation of the packaging ATPase activity of the motor, thus providing a direct link between structure and function. The implications of these results with respect to the assembly and activation of the functional packaging motor during a productive viral infection are discussed.
DOI: http://dx.doi.org/10.1016/j.bpj.2015.08.037
Dizem que Darwin varreu a teleologia completamente da biologia. Nada mais falso! Desonestidade acadêmica, pois o que mais se encontra nos abstracts de artigos e pesquisas é uma linguagem teleológica - é função a saltar aos olhos em todos sistemas biológicos complexos.
Função, que as pesquisas do Projeto ENCODE vieram cada vez mais fortalecer. E função é TELEOLOGIA. E, como bem disse Dan Graur, em uma de suas palestras:
"If ENCODE is right, then Evolution is wrong." [Se o ENCODE estiver certo, então a Evolução está errada].
Darwin, capice o que Graur disse sobre os resultados do Projeto ENCODE: se as pesquisas deste projeto atestam FUNÇÃO nos sistemas biológicos complexo, a Evolução já era. Kaput, Darwin!!!
Função, que as pesquisas do Projeto ENCODE vieram cada vez mais fortalecer. E função é TELEOLOGIA. E, como bem disse Dan Graur, em uma de suas palestras:
"If ENCODE is right, then Evolution is wrong." [Se o ENCODE estiver certo, então a Evolução está errada].
Darwin, capice o que Graur disse sobre os resultados do Projeto ENCODE: se as pesquisas deste projeto atestam FUNÇÃO nos sistemas biológicos complexo, a Evolução já era. Kaput, Darwin!!!
