Membrane Protein Function and Signaling

Vocabulary flashcards based on the lecture notes.

Structural Changes

Membrane proteins undergo these to facilitate function.

Receptor

Integral membrane protein that relays the primary message to the cell interior.

Secondary Messenger

Intracellular substance generated by the receptor to relay the primary message.

GPCRs

A family of membrane proteins with 7 transmembrane segments.

Kd (Dissociation Constant)

The constant that characterizes binding interactions, with a lower value indicating stronger binding.

Non-covalent Interactions

The type of interactions that influence binding affinity.

TM6

Movement in this transmembrane region transmits the signal inside the cell in the beta2-Adrenergic Receptor.

cAMP

Secondary messenger produced by the activation of adenylyl cyclase.

Protein Kinase A (PKA)

Enzyme activated by cAMP that phosphorylates and activates/inactivates other enzymes.

Ras Proteins

Superfamily of small GTPases involved in cell proliferation and apoptosis.

Enzyme-linked Receptors

Receptors that usually contain a single transmembrane segment and may dimerize upon ligand binding.

Phospholipases

Enzymes that hydrolyze phospholipids to produce 2nd messengers.

Insulin and Epinephrine

Two competing hormones mentioned in the lecture

Passive Diffusion

The process by which small, uncharged, or lipophilic molecules cross the membrane.

Facilitated Diffusion

Transport that requires the presence of binding sites on membrane proteins and is saturable at high substrate concentration.

Ion Channel Proteins

Membrane transporters that facilitate diffusion are also known as these.

TVGYG

Amino acid sequence that contributes to K+ binding in potassium ion channels.

Gly99

Amino acid that acts as a molecular hinge to open/close the potassium channel.

Beta Barrel Proteins

Integral membrane proteins composed of beta strands forming a pore in the membrane.

Active Transport

The movement of molecules against their concentration gradient.

Primary Active Transport

Active transport powered by the breakdown of ATP, light energy, or electron transfer.

Secondary Transporters

Transporters that use the gradient of one molecule to power the transport of another.

MsbA (Flippase)

Bacterial lipid transporter that moves phospholipids into the cell.

Bacteriorhodopsin

Protein found in Halobacterium salinarum that uses light energy to move protons out of the cell.

Retinal

Cofactor that contributes to the purple color of bacteriorhodopsin.

Proton Hopping

Process where protons are passed from one functional group to another, enabling rapid H+ ion mobility.

Bacteriorhodopsin

A seven-transmembrane protein with a retinal prosthetic group, covalently attached to Lys216 via a Schiff base.

Gα

Hormone signaling on the extracellular face induces a conformational change releasing the ____ subunit in the GTP bound state

GTP hydrolysis

Defects in ____ can lead to uncontrolled signalling and cancer.

β-adrenergic

Phosphorylation of the Insulin Receptor Substrate (IRS)-1 and activation of the pathway also leads to phosphorylation of the ____ receptor by Protein Kinase B (PKB).