generating diversity Flashcards
what is the priamry structure of a protein?
the sequence of amino acid that codes for a gene
what is the secondary structure of a protein?
folds of amino acid sequence to make alpha helices and beta pleated sheets
what is the tertiary structure of a protein?
overall 3D shape
what do alpha helices allow?
proteins able to insert into a membrane
beta pleated sheets
bonds that make up beta sheets are incredibly weak, however there are many of them, making it stronger
aggregation by beta pleated sheets with neurogenerative disorders
what is the quaternary structure of a protein?
multi-subunit assembly
the process of gene mutations result in…
related proteins with altered function
what does a point mutations result in?
altered primary sequence (e.g A swapped with G) by changing one nucleotide to a different one
effects= silence, misense and nonsense
how does insertion result in an altered primary sequence?
new nucleotides inserted resulting in different gene
how does deletion result in an altered primary sequence?
removes nucleotides resulting in a frame shift
gene duplication resulting in new proteins
not initially translated due to stop codon however if a poit mutation/deletion occurs in stop codon then there will be two copies of a single gene
what channels evolved by gene duplication?
sodium (duplicated 4 times) and calcium ion channels
relation of metabotropic glutatmate receptors
phyligenetic relation of G-protein coupled receptors fall into 3 groups that are dependent on sequence similarity and act ia different signalling mechanisms
group 1 of G-protein coupled receptors
mGluR1 and mGluR5
group 2 of G-protein coupled receptors
mGluR2 and mGluR3
group 3 of G-protein coupled receptors
mGluR7, mGluR4, mGluR8 and mGluR6
how many receptors are in the GPCR superfamily?
> 1200 receptors
quaternary structure adn ion channels
multiple individual proteins (monomers)
combine to form a ‘super-protein’ (multimer)
ion channels are multimeric assemblies
nAChR (nicotinic acteylcholine receptor) subunits?
5
NMDAR (glutamate receptors) subunits?
4
subunit composition
1=1
2=6
3=21
number of possible combinations increases with the number of available subunits and number of subunits required
GABAa receptor subunit composition
1000s of possible receptors from 13 genes but only a small number detected
alternative splicing
exon splicing can be variable e.g via exon skipping, creating splice variants (diffrential splicing)
alternative/diffrential splicing in the D2 dopamine receptors
there are 6 exons in the D2 receptors however sometimes exon 5 is not spliced
difference between D2 receptors
D2 (short) receptor is a pre-synaptic autoreceptor whereas D2 (long) receptor is post-synaptic
this is determined by a 29 amino acid insert in the long receptor
alternative splicing effects
has been found to be ubiquitous in eukaryotic cells (every single gene expressed is expressed in multiple ways)
e.g. in humans, ~95% of multiexonic genes may be alternatively spliced
DSCAM homologue from drosophila melanogaster (fruit fly) could have as many as 38,000 splice variants and it only has 15,000 genes
RNA editing (adenosine)
when you deaminate adenosine you create inosine, which is recognised by tRNA as guanosine
RNA editing explanation
enzymatic, post-transcriptional modification of RNA
most common form in eukaryotic cells is conversion of adenosine to inosine
results in codon change and so a change in protein 1o
sequence
