IGEM:MIT/2005/InsulinSensor

Members

1. Ray
2. Jessica

Goals

1. Detect CAP/CAMP
2. Determine CAP/CAMP transfer function vs. glucose
3. Universalize cAMP/CAP production given any input

Resources

Papers

• The relationship between external glucose concentration and cAMP levels inside Escherichia coli: implications for models of phosphotransferase-mediated regulation of adenylate cyclase. Authors: Notley-McRobb L, Death A, Ferenci T.

• Review:
  • Several hundred genes identified in E. coli regulated by cAMP/Crp complex (including lac and mal operons).
  • cAMP synthesis by adenylyl cyclase (AC) is the major regulatory site.
  • Detection of glucose levels by AC is incompletely understood but is approx. modelled as follows: in absence of glucose, members of the PTS system are normally phosphorylated, thus are continuously phosphorylating AC and driving cAMP production; in presence of glucose, members of the PTS system give up their phosphates to glucose and therefore primarily exist in nonphosphorylated forms, thus not stimulating AC and slowing cAMP production
  • Glucose transport DOES NOT correlate directly with AC activation. At medium levels of glucose, cAMP was still high despite PTS system working at saturation.
  • At low levels of glucose there is a second transition affecting cAMP levels, but it is different from strain to strain.
  • At low glucose levels, cAMP builds up inside to high levels and therefore has to be excreted (thus the transfer function of the extracellular cAMP closely resembles that of intracellular cAMP).
  • cAMP levels rise sharply when glucose levels drop to 0.3mM in minimal media (when PTS is working at 97% efficiency).

• CcpA-Dependent Carbon Catabolite Repression in Bacteria
• Review:
  • Carbon catabolite repression (CCR) follows different mechanisms in gram-postive and gram-negative bacteria
  • Gram positive uses CcpA dependent CCR
  • Gram negative uses cAMP-CRP
  • Gram postive modulates Ccpa with HPr as signalling itermediate
  • Gram negative uses EIIA-glc to activate adenyl cyclase and make cAMP. This is dependent on the phosphorylation state of EIIA-glc
  • Found homologies of CcpA signalling many proteobacteria and other types of bacteria

Books

• Regulatory networks in prokaryotes / edited by Peter Dürre and Bärbel Friedrich.
• The bacterial phosphotransferase system / edited by M.H. Saier Jr.

Questions/Suggestions/Input from other team members

Thought this might be of interest... -KBS

• Improvement of Escherichia coli production strains by modification of the phosphoenolpyruvate:sugar phosphotransferase system. Author: Gossett, G.

Diagrams

The PTS and components with which it interacts --JTN

http://www.horizonpress.com/hsp/supplementary/pts/fig1.gif