Computer Filename Protsyna ppt Protein Synthesis 1 Material

Computer Filename: Protsyna. ppt Protein Synthesis 1 Material for Introductory Microbiology

Overview þGenes are composed of DNA within the chromosome þGenes code for proteins þDNA is transcripted into RNA þRNA is translated into protein by ribosomes þGenes regulated by control of RNA production 2

Lecture Outline Protein synthesis þt. RNA structure adding amino acids to t. RNA þribosome structure þribosome attachment þprotein synthesis : initiation, elongation, attachment þ 3

Concepts from OAC þStructure & Function of DNA & RNA þGenetic code þTranscription & translation þProtein synthesis 4

Background Terms & Concepts *Structure of DNA & RNA þRibosomes þEnzymes 5

CODONS þ sequences of three adjacent nucleotides that 6 code for one amino acid or polypetide termination þ 64 codons encrypt of ~ 20 amino acids þ degenerate ACU, ACC, ACA, ACG threonine þ Start codon AUG (also codes for methionine) þ Stop codon UAA, UAG, UGA (nonsense codons)

Interpreting the Genetic Code þ Two step process : Transcription - translation þ Transcription DNA --> RNA þ Translation RNA--> protein 7

Transcription Production of an RNA copy of the gene þ occurs in nucleus þ DNA unravels- single strand þ RNA Polymerase binds to Promotor site þ Reads to stop codon þ assembles complementary single strand of RNA (primary RNA) þ Disengages when reaches stop codon 8

Ribosomal RNA þ called r. RNA þ found in Ribosomes þ catalytic site þ provides site for protein assembly þ ribosomal structure different in eukaryotes and prokaryotes 9

Prokaryotic ribosome þ 70 S þ large ribosomal subunit 50 S 1, 600, 000 34 proteins 5 S RNA 120 nucleotides 23 S RNA 2900 nucleotides þ Small ribosomal subunit 30 S 900, 000 21 proteins 16 s RNA 1540 nucleotides 10

Eukaryotic ribosome þ 80 S 4, 200, 000 þ large subunit 60 S 2, 800, 000 11 49 proteins 5 s RNA 120 nucleotides 28 s RNA 4700 nuclotides 5. 8 s RNA 160 nuclotides þ Small subunit 40 S 1, 400, 000 33 proteins 18 s RNA 1900 nuclotides

Transfer RNA þcalled t. RNA þSmaller than m. RNA or r. RNA þfound in cytoplasm þ 40 different kinds of t. RNA þtransports amino acids to ribosome þpositions amino acids polypeptide 12 on elongating

t. RNA 13

t. RNA 14

t. RNA Activating Enzymes þ Specific for each type of t. RNA þ called t. RNA synthetase þ binds to specific amino acid þ binds to specific nucleotides in t. RNA þ covalently þ 15 crosslinks amino acid to free 0 H water is lost

Large Ribosomal Subunit Two t. RNA binding sites 16

Polysomes 17

Ribosomes on Rough ER 18

EM of Ribosomes 19

Protein Synthesis þFormation of an initiation complex þChain elongation þChain termination 20

Concept Map: Protein Synthesis 21

Initiation of Protein Synthesis 22

Initiation 2 23

Initiation 3 24

Initiation 4 25

Internal Ribosome Entry Sequences Picro. RNA viruses cleave e. IF 4 g and use IRES 26