2.13.07 - 2.13.2007 In prokaryotes N-formyl methionine is...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
2.13.2007 In prokaryotes N-formyl methionine is the initial amino acid for polypeptides Doesn’t mean an AUG can never be found in the middle of the reading frame, just here there will be a regular methionine incorporated here N-formyl methionine is not found in eukaryotes ever, just regular methionine tRNA is one strand of RNA folded over itself o the 3’ end sticks up a little bit higher than the 5’ end and is called the 3’ acceptor stem to which an amino acid will be covalently attached o the 3’ acceptor stem is the location at which the amino acid that it carries is COVALENTLY attached, later on when it is broken it releases energy that is important o how does the amino acid get placed here? It is added on by an enzyme called amino acyl tRNA synthetase The two things that amino acyl tRNA synthetase puts together are tRNA and the amino acid 20 different amino acid, 40 something different tRNAs, what are the odds that an enzyme can do this that accurately, this is not one enzyme but is roughly 20 enzymes, there is roughly one amino acyl tRNA sythetase per amino acid Ex. Have praline amino acyl tRNA synthetase which can recognize any praline tRNA and the praline amino acid, some flexibility but it is a family of enzymes that are differently specific o Three nucleotides make up the anticodon which will base pair with the codon on the mRNA The whole loop is called the anticodon loop Within a loop there can be T, psi, etc, rare bases, the T, psi, and C in the loop is so highly conserved it is called the T, psi, C loop Within another loop there is a D loop with dihydrouracils in it o tRNA is not really clover shaped, the secondary shape is clover shaped, it actually gets folded along its vertical axis so what it is really doing is, its TpsiC loop is folded over interacting with the D loop, they interact with numerous weak bonds, this isn’t very stable though so the 3’ acceptor stem bends down at the same time anticodon is still at very bottom, so its really not a clover its an inverted L or boomerang in three dimensions o the way the two loops (TψC and D loop) interact reinforces that three D shape the rare bases of the tRNA have a function of increases translation’s accuracy and speed because the rare bases within the tRNA help to reinforce this shape, may go beyond this in that even within the shape these bases may also interact with the ribosome and function on the tRNA to enhance speed so the rare bases definitely help form the shape the shape helps contribute to speed and accuracy may extend beyond this scope as well, vague but generally what rare bases function for one of them, inosine we talk about later genetic code tells you which amino acids corresponds to which codons in the mRNA, you don’t memorize it o must know how to use it, know that on the chart the codons are written 5’ to 3’ and they are indeed codons, these are the sequences from the reading frame on the mRNA, if you look at the anticodon on the
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/07/2008 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

Page1 / 4

2.13.07 - 2.13.2007 In prokaryotes N-formyl methionine is...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online