-Turn Phe in HIV-1 Env Binding Site of CD4 and CD4 Mimetic Miniprotein Enhances Env Binding Affinity but Is Not Requi
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- 作者：Cynthia S. Dowd ; Stephanie Leavitt ; Gregory Babcock ; Alexis P. Godillot ; Don Van Ryk ; Gabriela A. Canziani ; Joseph Sodroski ; Ernesto Freire ; and Irwin M. Chaiken
- 刊名：Biochemistry
- 出版年：2002
- 出版时间：June 4, 2002
- 年：2002
- 卷：41
- 期：22
- 页码：7038 - 7046
- 全文大小：366K
- 年卷期：v.41,no.22(June 4, 2002)
- ISSN：1520-4995
文摘
HIV-1 enters a host cell after an initial interaction between viral envelope glycoprotein gp120and cell surface receptor CD4, followed by a second interaction between gp120 and a cell surface chemokinereceptor. CD4 residue Phe43 makes a significant contribution to the high-affinity interaction betweenCD4 and env. We and others have used scorpion toxin scaffolds to display and examine CD4 epitopesused for gp120 recognition. These peptides, which have a 
-turn Phe that acts as a Phe43 surrogate,compete with CD4 for gp120 binding and enhance the binding of gp120 to 17b, an antibody that bindsnear the co-receptor-binding site. In the current study, a scyllatoxin-scaffolded peptide, identified viaphage epitope randomization and lacking a -turn Phe (indeed, containing no aromatic residues), wasshown to behave in a distinctly CD4-like manner. This peptide, denoted [20EGLV23]ST, not only competedwith CD4 for gp120 binding, but also enhanced the binding of gp120 to 17b. Quantitatively, an[20EGLV23]ST-gp120 complex exhibited the same 17b binding on-rate as a complex of gp120 with[20AGSF23]ST, a scyllatoxin-based CD4 mimetic peptide containing a -turn Phe. In view of this result,we examined the role of Phe43 in CD4 itself by comparing F43V D1D2 sCD4 versus D1D2 sCD4. Likethe peptides, a close similarity was observed for both Phe43 and Phe43-less D1D2 sCD4s in enhancinggp120 binding to 17b. Further, when examined for their ability to enhance binding of gp120 to CCR5+cells, [20EGLV23]ST and [20AGSF23]ST were found to have the same efficacy, after correcting for thedifference in their gp120 affinities. These results show that, although Phe43 is important in maintaininghigh affinity in gp120 ligands, the aromatic residue is not necessary for triggering the conformationalisomerization in gp120 that results in formation or exposure of the binding sites for the 17b antibody andthe CCR5 receptor.
-turn Phe that acts as a Phe43 surrogate,compete with CD4 for gp120 binding and enhance the binding of gp120 to 17b, an antibody that bindsnear the co-receptor-binding site. In the current study, a scyllatoxin-scaffolded peptide, identified viaphage epitope randomization and lacking a -turn Phe (indeed, containing no aromatic residues), wasshown to behave in a distinctly CD4-like manner. This peptide, denoted [20EGLV23]ST, not only competedwith CD4 for gp120 binding, but also enhanced the binding of gp120 to 17b. Quantitatively, an[20EGLV23]ST-gp120 complex exhibited the same 17b binding on-rate as a complex of gp120 with[20AGSF23]ST, a scyllatoxin-based CD4 mimetic peptide containing a -turn Phe. In view of this result,we examined the role of Phe43 in CD4 itself by comparing F43V D1D2 sCD4 versus D1D2 sCD4. Likethe peptides, a close similarity was observed for both Phe43 and Phe43-less D1D2 sCD4s in enhancinggp120 binding to 17b. Further, when examined for their ability to enhance binding of gp120 to CCR5+cells, [20EGLV23]ST and [20AGSF23]ST were found to have the same efficacy, after correcting for thedifference in their gp120 affinities. These results show that, although Phe43 is important in maintaininghigh affinity in gp120 ligands, the aromatic residue is not necessary for triggering the conformationalisomerization in gp120 that results in formation or exposure of the binding sites for the 17b antibody andthe CCR5 receptor.