Histidine and HDH Functionality

• Attaching HDH to thiolase limits its function.
• HDH synthesizes histidine in the cytosol but not in the peroxisome.

Experimental Observations

• Experiment tracks the loss of function when HDH is tethered to thiolase.
• Parts of thiolase are removed to identify the peroxisome signal sequence.
• Removal of amino acids from positions 1-50 and 1-100 does not stop peroxisome targeting.
• Removal from positions 101-125 ceases targeting to the peroxisome, indicating those amino acids contain the signal.

Protein Structure and Targeting

• Protein structure: N-terminus and C-terminus defined by sequence position.
• Tails dictate nuclear localization; presence is sufficient but not necessary for proper localization.

Trafficking and Vesicle Dynamics

• Cargo triggers vesicle formation via binding to cargo receptors.
• Proteins move via motor proteins along microtubules, rather than floating.
• V snare (vesicle protein) and T snare (target membrane protein) ensure specificity in targeting and fusion.
• Fusion involves brute force from snares; dependent on membrane chemistry and physics (e.g., pH differences).

Protein Sorting Mechanisms

• Cargo proteins are packaged within vesicles for transport.
• Different conditions (high salt, detergent) are needed to extract membrane-associated proteins.
• Correct protein localization is crucial for cellular function; errors can result in proteins ending up in incorrect cellular areas.