Week 6 Bollough Lecture 11 Flashcards
What is secondary active transport?
Acts as a carrier protein
a) couple the thermodynamically unfavourable flow of one species of ion or molecule up a concentration gradient to the favourable flow of a different species down a concentration gradient
What is a carrier protein?
Carriers are proteins that transport ions or molecules across the membrane without hydrolysis of ATP
What is lactose permease?
An archetypal secondary active transporter
a) Secondary transporters are found right across bacteria, archaea and eukaryotes
How many helices are in lactose permease?
12, likely to have risen through duplication
What is the structure of lac permease (LacY)?
Two halves, each of which comprises six membrane-spanning α helices, confer a pseudo-symmetry structure.
a) The two halves are well separated and are joined by a long loop (TM6 and 7).
b) A sugar molecule lies in a pocket between the two halves and is accessible from a path that leads from the interior of the cell.
How does lacY work?
There is a low concentration out of the cell of lactose
a) When the proton binds LacY the affinity changes to high affinity of Lactose
b) Lactose then binds
c) The protein flips
d) Lactose leaves
e) Proton leaves
f) Protein flips back
Why is it important that lactose is only able to bind after the proton has bound
To be specific to lactose
a) to have the energy to flip the protein
