Adenylyl Cyclase

Overview/Structure

What does it do?

Overview- General Structure

• Lyase• Enzyme that converts ATP to cAMP• Interacts with g proteins and

receptors• 1064-1353 amino acids long• 120-150 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 (360-390 amino

acids)• C2a/C2b: large cytoplasmic domains (255-330 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

OverviewSignal 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

Activation

Activation

Catalysis Mechanism

ATP → cAMP +PPi

→ +

ATP cAMP pyrophosphate

Catalysis Mechanism

Catalysis Mechanism

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

Adenylyl CyclaseRegulation

GDP

GTP

RECEPTORADENYLYL 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

Ca2+ Regulation Site

CALCIUM/CALMODULIN

CA2+ ions

CALMODULIN

PKC (Protein Kinase C)

ReferencesThe University of Oklahoma College of Medicine. Human Physiology Animations Page

http://w3.ouhsc.edu/human_physiology/presentation/cyclaseani.gif (movie)

Western Kentucky University: Advanced Molecular Genetics http://bioweb.wku.edu/courses/ biol566/Images/gp009.jpg (both primary pics)

Saint Edward’s University. Structure of G-Proteins and Adenylyl Cyclases. http://www.cs.stedwards.edu

Hanoune, Jacques, et al. Adenylyl cyclases: structure, regulation and function in an enzyme superfamily. Molecular and Cellular Endocrinology 1997: (128) 179-194.

Tang, Wei-Jen and James Hurley. Catalytic Mechanism and Regulation of Mammalian Adenylyl Cyclases. Molecular Pharmacology 1998: (54) 231-240.

Sunahara, Roger et al. Complexity and Diversity of Mammalian Adenylyl Cyclases. Annual Review of Pharmacology Toxicology 1996: (36) 461-480.

Cann, Martin. Bicarbonate Stimulated Adenylyl Cyclases. Life 2004: (9) 529-534.