Plant Toxins Flashcards
what are the main toxins released from plants
ribosome inactivating proteins (RIPs)
how many types of RIPs are there
2
what is the main example of type 2 rip
ricin
what is the size of the A and B chains of ricin
3kDa
what is the function of the A chain
warhead
what is the function of the b chain
Binding
in what year was georgi markov killed in londn using ricin
1978
how many polupeptide chains do type 1 RIPs have
1
what is the first step in the mechanism of action of Ricin
bchain binds b-1,4-linked galactose in membrane glycoproteins and glycolipids which are common to all cells of the body
after binding the membrane, how does ricin endter the cell
by the endocytic pathway
what happens to ricin once it is endocytosed
it is transferred toearly endosomes
hwhat percentage of the toxin is recycled and degraded by lysosomes
95%
what happens to the 5% which is not degraded
transferred to the golgi network
where is ricin transported to from the golgi
ER
how is ricin transported to the ER
by binding a protein with KDEL sequence
once in the ER what occurs
reductive cleavage of disulphide bond
how/why is the A chain translocated into the ER
treated as a misfolded protein
how does the A chain block protein synthesis
it targets the 28s rRna of the 60s ribosomal subunit tand splits the glycosidic bond of one adenine base at a critical site causing the loss of binding of elongation factors
what other cytotoxic actions can the A chain carry out aside from DNA aand RNA deadenylation
lyase activity to catalyse the fragmentation of DNA
