5 - Pilus Biogenesis Flashcards
Why is pilus research of particular interest to medical science?
Bacteria such as E. coli rely on them for recognition and attachment to their target membrane.
Why is the type 1 pilus particularly important to investigate?
It is used by bacteria to attach themselves to the bladder where they cause UTIs.
Which bacterial pilus is used to attach to the kidney epithelium?
The P-pilus.
What is the general structure of a pilus?
A long inflexible pilus rod with a shorter, thinner and more flexible fibrillum tip that is responsible for recognition and binding.
What does the pap gene cluster encode?
The P pilus.
What subunits make up the pilus rod and fibrillum of the P pilus?
Pilus rod comprised entirely of papA.
Fibrillum made up of a variety of subunits, mostly papE but also K, F and G.
What role do papK and papF play?
They are the major adaptor proteins of the P pilus fibrillum.
What is the larger structure of the pilus subunits?
They are all similar to an immunoglobulin fold, but missing the C-terminal ß-strand (G-strand) that produces a groove in the superstructure.
How do the pilus subunits bind to each other?
Each one possesses an N-terminal sequence that can bind into the groove of the one before it by donating a beta strand to produce a full immunoglobulin fold.
What is the name of the way in which a pilin subunit recruits the next subunit by binding it into its groove?
ß-strand complementation.
What role does PapG play?
Forms the very tip of the fibrillum, containing a special binding domain on its extra immunoglobulin fold.
How are the pilus subunits transported into the periplasmic space?
After translation they are transported unfolded to the perplasmic membrane where they are recognised by the YEG transporter, which translocates them into the periplasmic space.
What occurs to the pap subunits when they reach the periplasmic space?
They fold into their immunoglobulin form, aided by a Periplasmic Disulphide Isomerase called DsbA. They are then bound by a molecular chaperone: papD.
What is the role of papC?
It is the usher protein that assembles the pilus out of the outer cell wall.
How is pilus formation initiated?
PapD binds to papG, being sandwiched between its immunoglobulin folds in such a way that the extra one enters the papC usher. The second papG domain then recruits the next subunit, F.
