The third variable loop or V3 loop is a part or region of the Human Immunodeficiency Virus. The V3 loop of the viron's envelope glycoprotein, gp120

Gp120

Envelope glycoprotein GP120 is a glycoprotein exposed on the surface of the HIV envelope. The 120 in its name comes from its molecular weight of 120 kilodaltons...

, allows it to infect human immune cells by binding to a cytokine

Cytokine

Cytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...

 receptor on the target human immune cell, such as a CCR5

CCR5

C-C chemokine receptor type 5, also known as CCR5, is a protein that in humans is encoded by the CCR5 gene. CCR5 is a member of the beta chemokine receptors family of integral membrane proteins...

 cell or CXCR4

CXCR4

C-X-C chemokine receptor type 4 also known as fusin or CD184 is a protein that in humans is encoded by the CXCR4 gene.- Function :...

 cell, depending on the strain of HIV

HIV

Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

.

This article was abstracted from the Wikipedia's main article on Human Immunodeficiency Virus, subsection on "Replication cycle: Entry to the cell".

External links

• The interactions of the gp120 V3 loop of different HIV-1 strains with the potent anti-HIV human monoclonal antibody 447-52D.