BIO282 Lecture Notes - Lecture 22: Guanine, Conformational Change, Sh2 Domain
SIGNAL TRANSDUCTION
Learning objectives:
In this topic/lecture you will learn about:
• Signal transductions and why cells need them
• Signal transduction mechanisms in bacteria
• Three major signal transduction pathways operating through
1. Receptors that have protein kinase activity
• Activation mechanism of these receptors
• Method of transmitting signal
2. Receptors that interact with a protein kinase
3. Receptors that interact with ‘G’ proteins
• Composition of ‘G’ proteins
• Method of signal transduction
• How small molecules generated through signal transduction affect gene expression.
• For something to enter the cell it needs to pass through the cell membrane
• However the cell membrane is hydrophobic meaning
• Only small ions, hydrophobic molecules and inorganic molecules can pass through
• Large molecules can't pass through the membrane though
• So how is a message communicated?
• Receptors
• The receptors has domains inside and outside the cell
• Any signal that comes (i.e. a ligand) binds to the extracellular domain, this causes a change in the receptor
on the cytosolic domain which creates a desired reaction inside the cell
• i.e. the molecule isn't passing through the cell membrane itself, but causing a chain reaction inside
the cell through its binding
• Signal transduction:
• processes involved in receiving a signal from the outside and converting it to make a functional
change inside the cell.
Signal Transduction in Bacteria
• Signal transduction pathways in bacteria regulate cellular functions in response to environmental signals.
Major systems that link environmental signals to cellular responses can be divided in following four
categories.
• Two component signal transduction systems (2CS)
• One component signal transduction systems (1CS)
• ECF sigma factor
• Class III adenyly/guanylyl cyclases
*Question: list three categories of the signal transductions in bacteria
• Here there are 2 proteins involved
• 1st protein is the sensor
• Senses the signal coming from the environment and transmits it to the regulator
• 2nd protein is the regulator
• The molecules that affects gene expression, and what gene will be expressed
• There are three components of the sensor
• Sensing domain
• Senses the signal (changes in the environment)
• Acceptor domain
• This is the domain that gets phosphorylated once the kinase/phosphatase domain is
activated by the sensing domain
• H - codes for histidine
• Kinase/phosphatase domain
• Kinase are responsible for adding a phosphate group (phosphorylation)
• Phosphatase can remove the phosphate
• This domain has both activities
• There are two components of the regulator
• Regulator domain
• The binding of DNA is controlled through the regulatory domain
• D - codes for aspartate
• DNA binding domain
• When a signal occurs from a stimulus, it is recognised by the sensing domain
• Through the use of ATP, the kinase/phosphatase domain is activated and causes the
phosphorylation of the acceptor domain
• The phosphate is then transferred from the histidine to aspartate
• Once the regulatory domain is phosphorylated the DNA-binding domain changes
affecting transcription
Document Summary
Three major signal transduction pathways operating through: receptors that have protein kinase activity, activation mechanism of these receptors, method of transmitting signal, receptors that interact with a protein kinase, receptors that interact with g" proteins. Composition of g" proteins: method of signal transduction, how small molecules generated through signal transduction affect gene expression. For something to enter the cell it needs to pass through the cell membrane: however the cell membrane is hydrophobic meaning, only small ions, hydrophobic molecules and inorganic molecules can pass through. Large molecules can"t pass through the membrane though. So how is a message communicated: receptors. Signal transduction: processes involved in receiving a signal from the outside and converting it to make a functional change inside the cell. Signal transduction pathways in bacteria regulate cellular functions in response to environmental signals. Major systems that link environmental signals to cellular responses can be divided in following four categories.
