Biological Membranes - A. N. Ogurtsov 2012

Electrogenesis of Biomembranes
Membrane Receptors
Insulin Receptor

Figure 149 shows the Insulin receptor. Unlike receptor Tyrosine Kinases, Insulin receptors are initially dimeric even in the absence of insulin. The exoplasmic domain of this receptor binds insulin, which leads to reciprocal tyrosine phosphorylation of the monomers by the receptor's kinase centers. Simultaneously, tyrosine residues on the accessory protein IRS-1 (insulin receptor substrate 1) are also phosphorylated.

Class="center">

Figure 149 - Scheme of insulin reception

Proteins containing SH2 domains can now attach to the phosphorylated tyrosines. One such protein, phosphoinositide 3-kinase (PI3-kinase), is activated (phosphorylated) As a result of this binding to the insulin receptor and, in turn, phosphorylates the membrane phospholipid phosphatidylinositol bisphosphate (PIP2) into phosphatidylinositol trisphosphate (PIP3) (Figure 43).

Just as SH2 domain-containing proteins bind to phosphorylated tyrosine, many proteins containing a so-called PH domain bind to PIP3, notably the cytosolic protein protein kinase B (PKB) (Figure 150).

Figure 150 - Scheme of protein kinase B activation

Protein kinase B is activated by phosphorylation. However, the kinase for PKB is a membrane protein and can only phosphorylate protein kinase B when the latter is bound to the membrane via PIP3.

Active PKB is required for the Vesicular Transport (see section 8.4) of membrane glucose transporter proteins (see section 6.5) from the Golgi apparatus membranes to Cell/30.html">The Plasma Membrane.

An increase in Blood glucose concentration stimulates the Pancreas to secrete insulin into the bloodstream. The binding of insulin to insulin receptors leads to The formation of PIP3 and, consequently, to the activation of protein kinase B and the intensification of vesicular transport of membrane glucose transporters to the plasma membrane, thereby increasing the influx of glucose into The Cell.

In addition to regulating transmembrane insulin transport, protein kinase B is also essential for numerous other cellular processes.

METABOLISM/35.html">Selection/41.html">Review Questions and tasks

1. What are the two distinct levels of signal perception and Transduction identified in Multicellular Organisms?

2. What are the three main levels of Regulation of the cellular response?

3. What four Methods of cellular response regulation exist at the protein level?

4. What three main Types of Membrane receptors are distinguished?

5. What is the autophosphorylating feature of receptor tyrosine kinases?

6. How is the protein SH2 domain structured, and what is its function?

7. How is the MAPK cascade organized?

8. What are the Similarities and differences in the functioning of MAPK, MAPKK, and MAPKKK Enzymes?

9. What are the similarities and differences between insulin and receptor tyrosine kinases?

10. What is the specific feature of membrane-bound activation of protein kinase B?



Last update: 13/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.