Lecture 3: Protein Structure and Function
January 15, 2013
Why is there no antenna around the photoreceptor when it around a photosystem?
if your a photosystem you just want to harvest all the light but in a photoreceptor you are
trying to harvest the light as information.
• Biological function is linked to proteins
• biochemistry came from trying to analyze proteins
• genetics studies genes
• two ﬁelds have come together to form MOLECULAR BIOLOGY
Protein abundance: Points of control
• control transcription (Dna to mrna)
• control of translation
• genes codes to protein
• mrna decay/turnover, this is controlled
Measuring Transcript Abundance
How do we measure one protein/rna?
• isolate RNA from cell or tissue samples (gel electrophoresis)
WHY DONT U C MRNA ON THE GEL?
• Abundance is much lower
• Rrna is 97% percent more abundant than Mrna (3%)
• Mrna moved to membrane, now the membrane can be probed and a single mrna can
• the probe is a radioactive gene-speciﬁc “probe”, it will hybridize to the single stranded
mrna, it is radioactive so it can be exposed to ﬁlm (northern blot)
Measuring Protein Abundance
• antibody is easy to detect
• the antibody sticks to a protein (western blot)
Heat Shock Response
• Chlamdomonas cells shifted from growth temperature of 24 degrees to 40 degrees
• transcript abundance is highest at 40 degrees
• actin is a house keeping protein not responsive to a change in t