week 6 Protein Targeting

Flashcards about Protein Targeting and Secretory Pathways

What is the central dogma of molecular biology?

DNA is transcribed to RNA, and some RNA (mRNA) is translated into protein.

What is protein targeting and secretory pathways about?

How proteins find their specific location in the cell for structure and function, including the secretion of proteins out of the cell.

What is the major structural difference between eukaryotic and prokaryotic cells?

Eukaryotic cells have organelles, while prokaryotic cells do not.

Name some organelles within a eukaryotic cell.

Endoplasmic reticulum (ER), Golgi body/apparatus, endosomes, lysosomes, and secretory vesicles.

Briefly describe protein trafficking in eukaryotes.

Proteins are made in the endoplasmic reticulum, processed in the Golgi apparatus, and transported to their functional location through protein trafficking.

What defines the organelles within a cell?

They have specialized contents and membranes with specific phospholipids and structural/functional proteins.

What is the specialized function of the Golgi apparatus?

Post-translational modification of proteins.

How do proteins get transported into the nucleus or across membranes?

Through nuclear pores or vesicle transport.

How do proteins 'know' where to go within the cell?

Encoded molecular clues within the molecules, specifically conserved amino acid sequences (signal peptides) on the N-terminal part of the protein.

What are the three regions of a signal peptide?

N-terminal region (positively charged amino acids), middle hydrophobic region (hydrophobic amino acids, often leucines, forming an alpha helix), and a C-terminal region (uncharged amino acids, possibly forming a beta sheet).

What proportion of proteins are actually secreted from a cell, 9% or 34%?

The proportion of proteins secreted from the cell.

What mechanism determines the direction and specificity of secretion, related to a 'lock and key' analogy?

Ligand-receptor interactions.

How is protein cargo transported around the cell?

Vesicle formation.

What determines the specificity of donor-acceptor vesicle interactions?

Proteins on the surface of the vesicles (ligand-receptor interactions).

Name three specific vesicle transport proteins (coat protein complexes).

Clathrin, COP1, and COP2.

What is the function of clathrin, COP1, and COP2?

Clathrin targets vesicles to the trans-Golgi network for transport to the endosome, COP1 targets vesicles from Golgi to the ER (retrieval pathway), and COP2 moves vesicles from the ER to the Golgi (forward pathway).

Which molecule is key in vesicles that transport cargo from the trans Golgi network to the endosome and beyond?

Clathrin

What accessory proteins increase the specificity of vesicle transport?

SNAREs

What family of proteins adds to the specificity of vesicle transport and powers the opening of the vesicle?

Small GTPase proteins (Rab family).

What are the processes of exocytosis and endocytosis?

Exocytosis involves the release of substances from inside a cell to the extracellular space via vesicle fusion, while endocytosis involves molecules being taken into the cell.