AH Biology: Unit 1 Proteomics and Protein Structure 4 Reversible Binding of Phosphate and Control of Conformation

Think What conditions are affected by the permanent activation of specific proteins? What is the charge on a phosphate group? What effect does phosphate have on protein? How is ATP generated by a cell? How is ATP used by a cell?

Kinase Kinase is often responsible for the phosphorylation of other proteins through ATP.

Kinase A phosphate group is highly charged, altering the position of charged bonding in the three-dimensional structure of the protein and as a result causing a conformational change.

Kinase Kinase animation 1animation 1 Kinase animation 2animation 2

Kinase Control of the cell cycle through cyclin dependent kinase Cdks.cell cyclecyclin dependent kinase Cdks Cyclins build up during the separate phases of the cell cycle and drive the cell into mitosis through the activation of different Cdks. Each Cdk phosphorylates different target proteins in the cell. Four classes of cyclin-Cdk: 1.G1-Cdk 2.G1/S-Cdk 3.S-Cdk 4.M-Cdk + mitosis promoting factor (MPF) Control of cell cycle game

Kinase Now read this article: –Knight JDR, Qian B, Baker D, Kothary R (2007) Conservation, Variability and the Modeling of Active Protein Kinases. PLoS ONE 2(10): e982. doi: /journal.pone Conservation, Variability and the Modeling of Active Protein Kinases –Use Proteomics Tutorial 1 and answer the targeted questions in relation to this article.

Phosphatase Phosphatase catalyses dephosphorylation of other proteins by the hydrolysis of phosphate from the protein molecule. This again changes the conformation of the protein as a result of charge interactions of the R groups in the protein. The cell cycle is finally pushed into the M phase by the phosphatase Cdc25. This removes an inhibitory phosphate from MPF, activating mitosis.

Phosphatase and glycogen metabolism Gluconeogenesis: –Glucose-6-phosphatase is an important enzyme involved in the dephosphorylation of glucose-6-phosphate produced from the metabolism of glycogen. –This generates glucose, which is then available for excretion from the cell or directly for respiration.generates glucose

Phosphatase and glycogen metabolism

Glucose-6- phosphatase system deficiencies

Signal transduction Extracellular hydrophilic signalling molecules are involved in the activation of extracellular receptor proteins that then interact with intracellular proteins through a series of kinases and phosphatases. This cascade of phosphorylation and dephosphorylation quickly activates intracellular events. Insulin and the blood sugar level are controlled in this way, as is cell death (apoptosis).blood sugarapoptosis G-protein-coupled signal transduction Cyclic AMP signalling

Kinase cascade

Sodium potassium pump

ATPases Sodium potassium pump animationSodium potassium pump Glucose co-transporter animation

Mitochondria

Aerobic respiration

Regeneration of ATP ATP is regenerated in respiration. Most respiration takes place in the mitochondria via oxidative phosphorylation.oxidative phosphorylation This creates a proton gradient that is used to drive the membrane-bound enzyme ATP synthase and thus produce ATP.

Skeletal/striated muscle and contraction using ATP

Transmission electron microscope image: human striated muscle

Sarcomere

A muscle contracts as the actin and myosin filaments slide past each other. The distance between the Z lines decreases during muscle contraction and as a result the muscle shortens. This can be seen in the muscle as the A bands remain the same length but the I band and H zone get shorter during the contraction. Sarcomere contraction animation

Muscle contraction via ATPase Myosin has heads that act as cross bridges as they bind to actin at specific binding sites and allow the muscle to contract.cross bridges

Muscle contraction via ATPase Breakdown of ATP and cross-bridge movement animation. Actin and myosin animation Actin and myosin animation: Harvard BioVisions in detailActin and myosin animation

Protein interactions in the cell The following animations illustrate the importance of protein in the control of the cell’s activities: –The Inner Life of the Cell: protein interactionsThe Inner Life of the Cell: protein interactions –pathways to cancer animationpathways to cancer animation –apoptosis animationapoptosis animation –cell signals animationcell signals animation

Think What conditions are affected by the permanent activation of specific proteins? What is the charge on a phosphate group? What effect does phosphate have on protein? How is ATP generated by a cell? How is ATP used by a cell?