[bioslawek]

Montaż i demontaż pilusa typu IV. Pilusy, to takie rurki, które umożliwiają bakteriom wymianę materiału genetycznego między sobą (koniugację) lub infekowanie innych komórek (w tym eukariotycznych) różnymi białkami. Istnieje kilka rodzajów pilusów i wszystkie wchodzą w skład nieredukowalnie złożonych maszyn molekularnych. TUTAJ biogeneza innego rodzaju pilusa: https://bioslawek.wordpress.com/2015/01/11/biogeneza-pilusa/

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Architecture of the type IVa pilus machine

SUPER! Irreducible complexity ( ͡° ͜ʖ ͡°)

Rotary Motor

The motor is thought to control whether the pilus is being extended or contracted at any moment. Individual pilin subunits are embedded in the membrane. A small asymmetric protein in the motor, termed PilC (colored red in the illustrations), has a cavity on one side that cups the end of the filament. Researchers have proposed that as the motor turns, PilC forces the filament up, opening space for a new pilin subunit to associate. To shorten the filament, the motor appears to switch direction, popping pilin subunits one at a time back into the membrane.

The pilin subunit has a distinctive structure. It has a globular head that is covered with charged, water-soluble amino acids (shown here in magenta), and a long alpha-helical tail that is mostly hydrophobic (shown in white). The hydrophobic tail plays two roles: it embeds the individual pilin subunits into the bacterial membrane, and it forms a tight bundle with other pilin subunits to stabilize the filament. To explore of pilin and the filament (PDB entry 2hil) in more detail, click on the image for an interactive JSmol; http://pdb101.rcsb.org/motm/211

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