Sistemas de inyección contráctil de bacteriófagos

Bacteria and bacteriophages utilize a  rigid  tube-contractile  sheath  mechanism  for delivering proteins and DNA across the cell envelope. Here we describe conserved features of these contractile assemblies and propose their evolutionary pathway. The complexity of today’s systems is a result of gene duplication and subsequent specialization of function.

Contractile    tail    bacteriophages, or    myobacteriophages, use    a    sophisticated biomolecular structure to inject their genome into the bacterial host cell.  This structure consists of a contractile sheath enveloping a rigid tube that is sharpened by a spike-shaped protein complex at its tip. The spike complex forms the centerpiece of a baseplate complex that terminates the sheath and the tube.  The baseplate anchors the tail to the target  cell membrane  with  the  help  of  fibrous  proteins  emanating  from  it  and  triggers  contraction  of  the sheath. The contracting sheath drives the tube with its spiky tip through the target cell membrane.  Subsequently, the bacteriophage genome  is  injected  through  the tube.  The structural transformation of  the  bacteriophage  T4  baseplate  upon  binding  to  the  host  cell  has  been  recently  described  in  near-atomic  detail. 

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