Protein Transport Mechanisms

Protein Transport Mechanisms

• Proteins may fold into their final form as they are synthesized and then move through an aqueous medium to their final destination, remaining folded throughout.
• Delivery of proteins to the nucleus occurs through gated transport, where proteins are synthesized on cytosolic ribosomes and pass through nuclear pores into the nucleoplasm.

Transmembrane Translocation

• Transmembrane translocation involves the transport of unfolded polypeptide chains across one or more membranes to reach their final destination.
• Proteins destined for the interior of peroxisomes, mitochondria, and chloroplasts are synthesized on cytosolic ribosomes, may fold partially, and are then unfolded for transport across the membrane.

Vesicular Trafficking

• Vesicles, small closed bags of membrane, carry newly synthesized proteins from the endoplasmic reticulum to the Golgi apparatus and between other compartments.
• The fate of a protein, whether to remain in the cytosol or be transported via an alternative path, is determined by sorting signals within the protein itself.

Targeting Sequences

• Initial sorting decisions are made based on particular amino acid sequences called targeting sequences.
• For proteins synthesized on the rough endoplasmic reticulum, additional sorting signals such as sugars and phosphate groups can be added by enzymes that modify the protein's chemical structure.

Protein Transport Mechanisms

• Proteins may fold into their final form as they are synthesized and then move through an aqueous medium to their final destination, remaining folded throughout.
• Delivery of proteins to the nucleus occurs through gated transport, where proteins are synthesized on cytosolic ribosomes and pass through nuclear pores into the nucleoplasm.

Transmembrane Translocation

• Transmembrane translocation involves the transport of unfolded polypeptide chains across one or more membranes to reach their final destination.
• Proteins destined for the interior of peroxisomes, mitochondria, and chloroplasts are synthesized on cytosolic ribosomes, may fold partially, and are then unfolded for transport across the membrane.

Vesicular Trafficking

• Vesicles, small closed bags of membrane, carry newly synthesized proteins from the endoplasmic reticulum to the Golgi apparatus and between other compartments.
• The fate of a protein, whether to remain in the cytosol or be transported via an alternative path, is determined by sorting signals within the protein itself.

Targeting Sequences

• Initial sorting decisions are made based on particular amino acid sequences called targeting sequences.
• For proteins synthesized on the rough endoplasmic reticulum, additional sorting signals such as sugars and phosphate groups can be added by enzymes that modify the protein's chemical structure.

Learn about the two main mechanisms of protein transport: gated transport and transmembrane translocation. Understand how proteins move to their final destinations in the cell.