Adenylyl Cyclase Overview/Structure

What does it do?

Overview- General Structure Lyase Enzyme that converts ATP to cAMP Interacts with g proteins and receptors amino acids long kilodaltons

General Structure cont’d 10 mammalian isoforms –All membrane bound –60% similarity –50%-90% in cytoplasmic regions

Primary Structure The main structural features of mammalian adenylyl cyclases M1/M2: 2 sets 6 transmembrane spans C1a/C1b: large cytoplamic domains ( amino acids) C2a/C2b: large cytoplasmic domains ( amino acids) –Most highly conserved sequence in all isoforms –50% similar; 25% identical N terminus and C terminus

Primary Structure Topology

Secondary Structure Alpha helices Beta sheets

Tertiary Structure The folding of a protein into a 3-D structure

Quaternary Structure Interaction between two domains Large cytoplasmic domains –C1a –C2b

Quaternary Structure Adenylyl cyclase interaction with G protein

Adenylyl Cyclase Function

Overview Signal Transduction -produces cyclic AMP from ATP -responds to a large number of receptors 10 Isoforms -allows a diverse response to the same or similar signals

Overview sAC is the tenth form of AC. It is soluble and only found in sperm

Forskolin Activation Forskolin - increases affinity - increases stability - enhances activity

Activation

Catalysis Mechanism ATP → cAMP +PP i → + ATP cAMP pyrophosphate

Catalysis Mechanism

Role of Cyclic AMP Step 1: activates protein kinases Step 2: protein kinases phosphorylate substrate proteins Step 3: activated substrate proteins regulate hormone production

Adenylyl Cyclase Regulation

GDP GTP RECEPTOR ADENYLYL CYCLASE

Regulation by Receptors Alpha-adrenergic receptors: - Stimulate Gi Proteins Beta-adrenergic receptors: - Stimulate Gs Proteins G Protein Coupled Receptor

G PROTEIN REGULATION (Guanine Nucleotide-Binding Protein)

ADENYLYL CYCLASE BINDING

Ca 2+ Regulation Site

CALCIUM/CALMODULIN CA 2+ ions CALMODULIN

PKC ( Protein Kinase C)

References The University of Oklahoma College of Medicine. Human Physiology Animations Page (movie) Western Kentucky University: Advanced Molecular Genetics biol566/Images/gp009.jpg (both primary pics) Saint Edward’s University. Structure of G-Proteins and Adenylyl Cyclases. Hanoune, Jacques, et al. Adenylyl cyclases: structure, regulation and function in an enzyme superfamily. Molecular and Cellular Endocrinology 1997: (128) Tang, Wei-Jen and James Hurley. Catalytic Mechanism and Regulation of Mammalian Adenylyl Cyclases. Molecular Pharmacology 1998: (54) Sunahara, Roger et al. Complexity and Diversity of Mammalian Adenylyl Cyclases. Annual Review of Pharmacology Toxicology 1996: (36) Cann, Martin. Bicarbonate Stimulated Adenylyl Cyclases. Life 2004: (9)