<prompt> True about gp. 120 is?Virus attachmentVirus penetrationVirus detachmentVirus dissemination  <response>: ANSWER: A Virus attachmentREF: Jawetzs 24th ed chapter 44. AIDS LentivirusesEnvelope glycoprotein GP120 or gp 120 is a glycoprotein exposed on the surface of the HIV envelope. The 120 in its name comes from its molecular weight of 120 kilodaltons.The SU gp 120 product of the envgene contains binding domains responsible for virus attachment to the CD4 molecule and coreceptors, determines lymphocyte and macrophage tropisms, and carries the major antigenic determinants that elicit neutralizing antibodies. The gp 120 subunit is on the outside of the cell, and gp 41 is a trans-membrane protein. The TM gp 41 env product contains both a trans-membrane domain that anchors the glycoprotein in the viral envelope and a fusion domain that facilitates viral penetration into target cells. 