2. Lecture4
Synthesis of Proteins

3. The Three Roles of RNA in Translation
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)

4. Universal Genetic Code
Degeneracy:
a particular amino acid can be
specified by multiple codons.
Codon usage bias:
refers to differences in the
frequency of occurrence of
synonymous codons in coding DNA

6. The Folded Structure of tRNA Promotes Its Decoding Functions
Some different tRNAs have been identified in bacterial cells and as many as in animal and plant cells.

7. aminoacylation of tRNAs
The conservation of the genetic code suggests that aminoacyl-tRNA synthetases evolved early and were possibly among the first protein enzymes to emerge from the RNA world

8. Nonstandard base pairing at the wobble position

10. Initiation Selection of the initiating AUG is facilitated by specific
surrounding nucleotides called the Kozak sequence,
(5') ACCAUGG (3').

11. Elongation

12. Termination

13. Polysomes and Rapid Ribosome Recycling Increase the Efficiency of Translation

14. Purifying, Detecting, and Characterizing Proteins
A protein must be purified before its structure and the mechanism of its action can be studied.
The two most widely used characteristics for separating proteins are size, defined as either length or mass, and binding affinity for specific ligands.

15. Centrifugation
Proteins vary greatly in mass but not in density. Unless a protein has an attached lipid or carbohydrate, its density will not vary by more than 15 percent from 1.37 g/cm3, the average protein density.
Differential Centrifugation
Rate-Zonal Centrifugation
Isopycnic centrifugation

16. SDS-polyacrylamide gel electrophoresis (SDS-PAGE)

17. Two-Dimensional Gel Electrophoresis