Class Notes (810,969)
Canada (494,410)
Biochemistry (847)


3 Pages
Unlock Document

Western University
Biochemistry 2280A
Derek Mc Lachlin

Brandl Lecture 4 Notes 11/14/2012 Types of Mutations  Missense mutation – results in a single amino acid change o May or may not have affect on the protein  Frameshift mutation – insertion or removal of bases o Insertion or deletion of a base results in a change in reading frame of the protein from the point of mutation onward  Nonsense mutation – results in premature termination of the protein o Usually have functional consequence, truncates protein from that point onwards tRNA  Transfer RNA  Bring the amino acid to the growing polypeptide chain  All tRNAs have a similar structure  All approximately 80 bases in length  Nonconventional bases o Put in post-transcriptionally  2D cloverleaf structure due to internal base pairing (stems and loops) o Three loops – T loop, D loop, anticodon loop o All RNAs have complex structures as they are single stranded  2 key single stranded regions o 3’ acceptor site – is at the 3’ end which is the region that attaches to the amino acid  All tRNAs end with CCA, that is added post-transcriptionally o Anticodon – base pairs with the codon  In 3D, the tRNAs look like an L Wobble  Most organisms have fewer than 45 different tRNAs  How can all 61 amino acid encoding codons be used?  Some tRNA species must pair with more than one codon  Molecular basis for Wobble: o Base pairing between the anticodon of some tRNAs and the codon, only requires matching at two positions  Example – Phe has two codons (UUC and UUU) o Base pairing interactions for the two Phe codons, with the Phe-tRNA  Accurate base pairing at all 3 positions of the codon  Wobble – accurate base pairing at only the first two positions of the codon Aminoacyl tRNA Synthetases  Couple the 3’ end of a specific tRNA to a specific amino acid  There are 20 aminoacyl tRNA synthetases – one for each amino acid  Specificity is crucial  Charging of tRNAs o Must exquisitely recognize the amino acid and tRNA o Store energy from ATP in a high energy ester linkage  High energy bond between amino acid and tRNA o Energy is used later on for translation o Provide specificity by coupling an amino acid with its correct tRNA – proofreading function  No further check after this coupling Ribosomes  Catalyze protein synthesis  There are two subunits – large subunit and small subunit o Large subunit – 49 proteins and 3 RNA molecules o Small subunit – 33 proteins and 1 RNA molecule  RNA plays a key role structurally and in catalysis o RNA has catalytic activity, not the protein  There are three sites for the binding of tRNAs on the ribosome o A site, P site, and E site o A site – the site that binds aminoacyl-tRNA
More Less

Related notes for Biochemistry 2280A

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.