Ribosomes
- Created by: Amber Manley
- Created on: 09-01-14 11:40
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- Ribosomes
- what are they
- made of 2 subunits
- larger 60S unit
- has catalytic site
- 49 proteins
- smaller 40S subunit
- 33 proteins
- 2/3 RNA, 1/3 proteins
- larger 60S unit
- RNA core with proteins attached to it
- made of 2 subunits
- How are they made
- rRNA
- synthesis and processing
- ribosmoal proteins
- transcription, translation
- ribosmoal subunits
- assembly
- rRNA
- Nucleolus
- discrete area within the nucleus, no additional membrane
- Forms around parts of the chromosomes called nucleolar organisers
- site of ribosomal subunit production
- Nucleolar organiser
- Involves 10 chromosomes in humans
- 200 copies or rRNA genes
- nucleolus associated with chromosomal regions that contain rRNA genes
- Dense fibrillar component (RNA being transcribed)
- granular component (maturing ribosomes)
- fibrillar centre (DNA not being transcribed)
- Translation
- Initiation
- ribosomes recognise and bind to the 5' terminus
- Scan down mRNA until encounter a start codon
- involves small subunit
- elongation
- large subunit joins complex
- polypeptide chain elongates (addition of amino acids)
- 3 binding sites
- p- peptidyl
- a- aminoacyl
- e- exit
- initiator tRNA binds to p site
- next tRNA with anticodon complementary to the next codon binds to a site
- relies on base pairing of codons and anticodons
- termination
- stop codon is recognized by release factors in the cell
- stimulate hydrolysis of bond between tRNA and the polypeptide chain
- Initiation
- Protein turnover
- removal of misfolded proteins
- newly synthesised but misfolded are quickly degraded
- aging proteins
- failure to remove these proteins can interfere with normal cell functions
- How
- ATP dependent protease
- hollow tube of many subunits
- multi unit cap structures at each end (gateways)
- cap has ATPase activity, unfolds target protein
- substrate retained until degraded
- Control
- ubiquitin can be attached NH2 side chains of lysine residues targeted for degradation
- activated by binding to ubiquitin activating enzyme
- transfered to ubiquitin ligase
- E2E3 complex recognises targeted protein
- Ub added to protein, further Ub added by E1
- signal for degradation
- removal of misfolded proteins
- what are they
- rRNA Production
- Ribosomes
- what are they
- made of 2 subunits
- larger 60S unit
- has catalytic site
- 49 proteins
- smaller 40S subunit
- 33 proteins
- 2/3 RNA, 1/3 proteins
- larger 60S unit
- RNA core with proteins attached to it
- made of 2 subunits
- How are they made
- rRNA
- synthesis and processing
- ribosmoal proteins
- transcription, translation
- ribosmoal subunits
- assembly
- rRNA
- Nucleolus
- discrete area within the nucleus, no additional membrane
- Forms around parts of the chromosomes called nucleolar organisers
- site of ribosomal subunit production
- Nucleolar organiser
- Involves 10 chromosomes in humans
- 200 copies or rRNA genes
- nucleolus associated with chromosomal regions that contain rRNA genes
- Dense fibrillar component (RNA being transcribed)
- granular component (maturing ribosomes)
- fibrillar centre (DNA not being transcribed)
- Translation
- Initiation
- ribosomes recognise and bind to the 5' terminus
- Scan down mRNA until encounter a start codon
- involves small subunit
- elongation
- large subunit joins complex
- polypeptide chain elongates (addition of amino acids)
- 3 binding sites
- p- peptidyl
- a- aminoacyl
- e- exit
- initiator tRNA binds to p site
- next tRNA with anticodon complementary to the next codon binds to a site
- relies on base pairing of codons and anticodons
- termination
- stop codon is recognized by release factors in the cell
- stimulate hydrolysis of bond between tRNA and the polypeptide chain
- Initiation
- Protein turnover
- removal of misfolded proteins
- newly synthesised but misfolded are quickly degraded
- aging proteins
- failure to remove these proteins can interfere with normal cell functions
- How
- ATP dependent protease
- hollow tube of many subunits
- multi unit cap structures at each end (gateways)
- cap has ATPase activity, unfolds target protein
- substrate retained until degraded
- Control
- ubiquitin can be attached NH2 side chains of lysine residues targeted for degradation
- activated by binding to ubiquitin activating enzyme
- transfered to ubiquitin ligase
- E2E3 complex recognises targeted protein
- Ub added to protein, further Ub added by E1
- signal for degradation
- removal of misfolded proteins
- what are they
- Transcription
- Transcribed by RNA polymerase I
- high rate of transcription
- Formation
- 45S cleaved into 3 segments
- 5'-3' direction, amino to carboxy
- Large Subunit
- transcribed by RNA Pol III
- Made from 2 of the 3 segments
- Small subunit
- 55 structural proteins
- transcribed by RNA Pol II
- subunits are transported into cytoplasm for their role
- Ribosomes
- precursor RNA (45S) is processed
- Transcription
- Transcribed by RNA polymerase I
- high rate of transcription
- Transcription
- control of regulatory proteins
- maintained at low levels by short half life
- can be conditional
- stabilised when needed, degraded when not
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