Chapter 9 Flashcards
What are the challenges of envelope synthesis?
(4 problems in synthesis, plus one other thing)
Very complex- barrier, but also a direct interface with the outside world.
Problems in synthesis:
- Must be continuous, but also must allow growth
- Growth must be coordinated
- Constituents must be properly located
- Envelope must facilitate division
- Respond to environment
What is building the cell envelope about (3) ?
- making lipid membrane
- proteins exported across the cell envelope
- building complex cell envelope structures
Diagram of how lipids and proteins are inserted into the membrane:
Membrane- lipids inserted; proteins inserted.
Diagram of direct insertion:
Diagram of signal sequence-mediated insertion:
How do sec proteins work?
Protein secretion: secreting unfolded proteins through membrane and insertion of proteins into membrane
Diagram of gram negative outer membrane, and regulation of sec proteins:
Signal sequences:
N-terminal extensions of nascent polypeptide chains that mediate protein targeting to the membrane of the endoplasmic reticulum (ER)
Type 1
Type 2
Type 3
Type 4
Type 5
Type 6
How many types of systems are there?
9
Where is murein assembled (cell wall)?
Undecaprenyl cycle
Process of murein assembly:
- precursors (disaccharide-associated with pentapeptide) assembled in cytoplasm
- transport across membrane by lipid 2 and flippase
- assembly into pre-existing cell wall
Role of transglycosidases?
Polymerize precursors
Role of transpeptidase?
These are penicillin-binding proteins.
Attach peptide chains to form a strong meshwork.
Envelope synthesis: Outer membrane (gram-negative)
- Asymmetry
- LPS on the outside of the membrane
- lipids, proteins exported, inserted
BAM complex
