Explain how a type I secretion system works. Are the secreted proteins ever in periplasmic space?
Type I Secretion System (T1SS)
Almost all pathogenic bacteria contain T1SS. Sec-independent type I pathway goverens the secretion of some exoenzymes and toxins. The proteases produced by E. chrysanthemi, is governed by the type I secretory apparatus comprising of three accessory proteins (Prt D, E, and F).
In gram-negative bacteria, type I secretion is carried out by a translocator made up of three proteins that span the cell envelope. One of these proteins is a specific outer membrane protein (OMP) and the other two are cytoplasmic membrane proteins: an ATP-binding cassette (ABC) and the so-called membrane fusion or adaptor protein (MFP). Type I secretion is sec-independent and bypasses the periplasm. This widespread pathway allows the secretion of proteins of diverse sizes and functions via a C-terminal uncleaved secretion signal. This C-terminal secretion signal specifically recognizes the ABC protein, triggering the assembly of the functional trans-envelope complex. This report will mainly deal will recent data concerning the structure and assembly of the secretion complex as well as the effects and role of substrate folding on secretion by this pathway.
Gram-negative bacteria are surrounded by two membrane bilayers separated by a space termed the periplasm. The periplasm is a multipurpose compartment separate from the cytoplasm whose distinct reducing environment allows more efficient and diverse mechanisms of protein oxidation, folding, and quality control. The periplasm also contains structural elements and important environmental sensing modules, and it allows complex nanomachines to span the cell envelope. Recent work indicates that the size or intermembrane distance of the periplasm is controlled by periplasmic lipoproteins that anchor the outer membrane to the periplasmic peptidoglycan polymer. This periplasm intermembrane distance is critical for sensing outer membrane damage and dictates length of the flagellar periplasmic rotor, which controls motility.
Explain how a type I secretion system works. Are the secreted proteins ever in periplasmic space?
5. How could a secretion system like some of the type IV systems secrete DNA when these systems mostly secrete proteins? (Hint: the first step in conjugation covalently attaches a protein to one strand of the nicked DNA.) How could you show that this explanation of DNA transfer by a protein secretion system is correct?
QUESTION 21 These proteins, often injected into host cells by a type 3 secretion system, allow certain bacteria to penetrate cells by inducing phagocytosis of the bacteria by the host cell. As a result, these bacteria don't have to compete for nutrients and can resist many body defense molecules. This is used as a virulence factor by Shigella, Yersinia, and Salmonella. This best describes what? Bacterial flagella and axial filaments. Bacterial cell surface proteins called adhesins. Bacterial capsules (glycocalyces). Bacterial...
4. Ex plain how proteins produced in the rough endoplasmic reticulum can be secreted into the extracellular environment without ever crossing the plasma membrane. Use the terms rough endoplasmic reticulum ribosome, lumen, Golgi apparatus, cell membrane in your answer.
(c) Would a Type II secretion system, like that used by V. cholerae for secretion of cholera toxin, be an effective system to secrete teixobactin from Eleftheria terrae? Explain your answer. (3)
Consider cargo proteins that are destined for secretion to the extracellular space. Please predict where the cargo will end up (ex. in the cytoplasm, a specific organelle, transport vesicles, multiple places, extracellular space) for: (i) & (ii) Each individual condition; & (iii) The combination of both conditions. A. (i) Normal Sar1 is mutated so it binds tightly to GDP and cannot exchange it for GTP. (This leads to Sar1-GDP being the only form of the protein in the cell.) (ii)...
QUESTION 39 Which best describes a type 3 secretion system? A system that allows bacteria to transfer virulence factors from one bacterium to another by horizontal gene transfer. A system that enables bacteria to directly injecting bacterial effector molecules into the cytoplasm of the host cell in order to alter its cellular machinery or cellular communication. A system that allows bacteria to sense their own population density by communicating with each other by way of secreted chemical factors and behaving...
Describe how thyroid hormone secretion is regulated. Explain how this system is affected by (a) iodine deficiency and (b) ingestion of thyroid hormone pills
If you clone a structural genes of the Yersinia pestis type III secretion system into harmless E. coli, knowing that this E. coli strain will not become a human pathogen. Please give and explain the two causes for this.
1. Explain why PTH would be secreted in response to hypocalcemia. How will it fix the problem? What electrolyte imbalances could be caused by over-secretion of PTH? 2. Name the three principal buffering systems of the human body. How quickly do they take effect? How powerful are they? 3. Diabetics whose diabetes is not controlled may suffer diabetic ketoacidosis (DKA). Why does this occur? In what way would the respiratory system compensate for DKA? 4. Which of the following CANNOT...
31. In the digestive system, some protease enzymes must be secreted as an inactive form and then activated later by proteolytic cleavage once outside of the secreting cell to prevent active proteases from damaging the secreting cells. What is the category of precursor proteins of this type? Select one: a. glycosides b. zymogens c. ubiquitins d. activins