Altklausur

• nuclear transformation

• plastdidic transformation

• two plasmids are needed for E.coli:

  transfer and cargo

• cargo plasmids (later episomes) need an oriT (origin of transfer for E.coli)

• replication in diatoms: episomes need a centromer region, sequences from yeast are working

• episomes need two selection markers: for E.coli and for diatoms and MB1 ori = bacterial ori of replication

• after conjugation grwoth under phleomycin (antiobtic against bacteria, since E.coli dies because KmR does not protect) and selection marker succesful transfection of diatoms

• usual tests via PCR, sequencin etc.

• Nom Photochemical Quenching (NPQ)

• theory: always an even distribution of the excitation energy due to antenna movement

• plastiquinone redox state (PQ/PQH2) regulates the LHCII-kinase activity

  
  

  
  

  
  

• balamcing electron ransfer PSI - PSII: State tramsition

• two plasmids are needed for E.coli:

  transfer and cargo

• cargo plasmids (later episomes) need an oriT (origin of transfer for E.coli)

• replication in diatoms: episomes need a centromer region, sequences from yeast are working

• episomes need two selection markers: for E.coli and for diatoms and MB1 ori = bacterial ori of replication

• in CP29> Chl/zea

• in LHCII > Chl/lut

• aggregated LHC > Car/Chl or Chl/Chl

• Envelope import

• Thylakoid Transport and Insertion

• Import into complex

1. Envelope Import (Primary Plastids)

Nuclear-encoded proteins destined for the chloroplast are translated on cytosolic 80S ribosomes and must cross the double envelope.

• TIC/TOC Complex: The TOC (Translocon on the Outer Chloroplast membrane) and TIC (Translocon on the Inner Chloroplast membrane) complexes facilitate this passage.

• Requirements: This process depends on energy and is assisted by chaperones to keep proteins in an unfolded state for transport.

• Targeting Signal: Proteins possess a Transit Peptide (cTP), which is typically long and conserved, to be recognized by the envelope receptors.

2. Thylakoid Transport and Insertion

Once in the stroma, proteins targeted for the thylakoids utilize four distinct pathways based on their structure and folding state:

• Spontaneous Pathway: This is used for simple proteins with a maximum of two transmembrane helices.

• cpSRP Pathway: The chloroplast Signal Recognition Particle (cpSRP) pathway targets membrane proteins with more than two helices, such as LHCII and CP43. This pathway requires GTP and is regulated by the proton gradient ().

• Sec Pathway: Homologous to the bacterial secretory system, it translocates unfolded proteins across the thylakoid membrane. It is an energy-intensive process requiring ATP.

• Tat Pathway: The Twin-Arginine Translocation (Tat) pathway is unique because it can transport already folded proteins. It is driven solely by the proton gradient ().

3. Import into Complex (Secondary) Plastids

In organisms like diatoms and cryptophytes, plastids are surrounded by three or four membranes, requiring a more complex import system.

• Bipartite Signal: Proteins require a two-part targeting sequence: a Signal Peptide (S) for entry into the Endoplasmic Reticulum (ER) and a Transit Peptide (T) for plastid entry.

• ERAD Machinery: These organisms have adapted the ER-associated degradation (ERAD) machinery to instead function as a transport system to move proteins across the periplastidic membrane.

• Co-translational Transport: The outermost membrane is often connected to the nuclear ER, allowing for co-translational protein insertion

• by the tic/toc complex

• there are further transport systems concenring the envelope, also for envelope proteins themselves

• proteins of the thylakoid membrane or lumenal proteins have a thylakoid doimain in additoíon

• turnover of D1 protein: 30 min

top transcription

bottom translation