Metal Stress Flashcards
What are metalloenzymes
Essential metals are cofactors for catalytic acitity and occur in six enzyme comission classes such as oxidoreductases transferaases hydrolase lyases isomerase and ligase
What is the most prelevant metal to least
Mg Zn Fe and Mn
What is toxicity caused by
Interacation with SH and other functional groups displacement of essential metal cofactors and binding with certain protiens
What are common toxic effects
Carcinogenicity, Immune system impariment, Neurotoxicity, impariment of kidney, respiratory system
What is a structural motifi
Particular combination of two or more secondary structures that form a distinc three-dimensional structure when it apperas in mutiple protiens
What is zinc fingers composed of
Two antiparallel B strands with two cys followed by an a helix with two histindines
Zinc ion is coordinated by four amino acid residuces that results in the finer shapre the stabilzation of protien doamin (three secondary structure in zinc ion
What is the C4 zinc finger
Four conserved cysteines in contact with the Zn ion which is less common
Where does the recognition between the zinc finger and DNA occur
In the major groove the protien wraps around the DNA double helix
Which finger does not interacts with DNA
Finger one
What does the cell activate with heavy metal load
Metal stress response pathway associated with metal regulatory transcripton factor 1 which binds to MREs enahnces metallothiones and metal transporters
What are the 5 different functional domains of MTF-1
Dna binding domain, siz C2H2 zinc fingers
Nuclear import signal (NIS) domain
Nuclear export signal (NES)
Three transactivation domains
Homodimerization domain
What does activation of MTF-1 need
Loading with zinc, dimerization and post-translational modification by phosphorylation
What is happening under normal conditions to MTF-1
It is shuttling between the cytoplasm and nucleus which is mediated by interacation of MTF-1 with Crm1 mediated nuclear export of protiens taht carry a leucine rich NES
How is MTF-1 activated
Directly or indircetly by zinc released from protiens called metallothionens upon competive heavy metal load or oxidative stress
What is essential is MTF-1
All 6 zinc finger are lodaded with zin and phosphorylation
What happens after zinc binds
Dimerization and phosphorylation MTF1 shuttles to nucleus where it binds to MRE which is important for maintain metal homeostasis and detoxication of heavy metals
What else can MTF-1 help with
Against hypoxia hyperthermia and oxidative stress
What was the experiment with subcellular distribution
Kidney cells were transfected with VSV tagged MTF-1 and fluro untreated cells have mostly cytoplasmic localization of MTF-1 while the transcrption factor moves to the nucleus in cells treated with heavy metal
What does leptomycin B do
Can be stimilated by this drug which inihibits NES binding site of the nuclear export protien CRM1 induces nuclear accumulation of MTF-1 without affectin nuclear import
What plays a role in heat shock and other stress conditons
MTF-1 plays a role in regulating mutiple cellular stress response
What genes are important
Ones that are induced by MTF-1 and are required for maintatin metal homeostasis and detoxification of heavy metals are genes encoding meallothiones
What are metallothioneins
Cystenine-rich, low molecular weight intracellular metal binding protiens
What is the structure of metallothioneins
how many mental or atom
Consist of two domains alpha and beta which can bind 4 or 3 atoms of metal ions
What is the binding affinity
Zn < Cd< Cu<Ag = Hg =Bi
What does binding affinity mean
Cd will replace zn which will be avialble to load and activate MTF-1 which is the detoxication of non-essential metals such as cadium and the regulation of intracellular concentration of essentials metals such as Zn and Cu
