Martin Rodbell Signal Transduction in cells Through G-proteins

Martin Rodbell – discoverer of G-protein cell signal transmission

Article on martin rodbell

Biography & Contributions

Martin Rodbell was an American biochemist, molecular endocrinologist and Nobel Prize laureate born on December 01, 1925 – died on December 07, 1998. Martin is best known for his work on natural signal transducers called G-proteins that help cells in the body communicate with each other.

Rodbell discovered that ATP (adenosine triphosphate) could reverse the binding action of glucagon to the cell receptor and thus dissociate the glucagon from the cell altogether. Rodbell discovered that cellular communications also involved guanosine triphosphate (GTP). He asserted that individual cells were analogous to cybernetic systems made up of three distinct molecular components: discriminators, transducers, and amplifiers.

Guanosine Diphosphate

Guanosine Diphosphate is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside guanosine. It consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase guanine. It is the product of GTP dephosphorylation by GTPases, e.g., the G-proteins that are involved in signal transduction.

Adenosine Triphosphate

Adenosine Triphosphate (ATP) is a nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. Adenosine Triphosphate transports chemical energy within cells for metabolism. It is one of the end products of photophosphorylation, cellular respiration, and fermentation and used by enzymes and structural proteins in many cellular processes, including biosynthetic reactions, motility, and cell division.

One molecule of ATP contains three phosphate groups, and it is produced by a wide variety of enzymes, including ATP synthase, from adenosine diphosphate (ADP) or adenosine monophosphate (AMP) and various phosphate group donors. Substrate-level phosphorylation, oxidative phosphorylation in cellular respiration, and photophosphorylation in photosynthesis are three major mechanisms of ATP biosynthesis.

Adenosine Triphosphate is used as a substrate in signal transduction pathways by kinases that phosphorylate proteins and lipids. It is also used by adenylate cyclase, which uses ATP to produce the second messenger molecule cyclic AMP.

Adenosine Triphosphate is highly soluble in water and is quite stable in solutions between pH 6.8 and 7.4, but is rapidly hydrolysed at extreme pH. It composed of an adenine ring and a ribose sugar and three phosphate groups (triphosphate). The phosphoryl groups, starting with the group closest to the ribose, are referred to as the alpha (α), beta (β), and gamma (γ) phosphates.

It can also be synthesized through several so-called "replenishment" reactions catalyzed by the enzyme families of nucleoside diphosphate kinases (NDKs), which use other nucleoside triphosphates as a high-energy phosphate donor, and the ATP: guanido-phosphotransferase family. It is critical in signal transduction processes. It is used by kinases as the source of phosphate groups in their phosphate transfer reactions.

Adenosine Triphosphate is also used by adenylate cyclase and is transformed to the second messenger molecule cyclic AMP, which is involved in triggering calcium signals by the release of calcium from intracellular stores.

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