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Journal of Virology, April 2005, p. 4533-4539, Vol. 79, No. 7
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.7.4533-4539.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

The Conserved Glycine-Rich Segment Linking the N-Terminal Fusion Peptide to the Coiled Coil of Human T-Cell Leukemia Virus Type 1 Transmembrane Glycoprotein gp21 Is a Determinant of Membrane Fusion Function

Kirilee A. Wilson,1,{dagger} Séverine Bär,2 Anne L. Maerz,1 Marc Alizon,2 and Pantelis Poumbourios1*

St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia, and,1 Department of Cell Biology, Institut Cochin, Paris, France2

Received 30 August 2004/ Accepted 19 November 2004

Retroviral transmembrane proteins (TMs) contain an N-terminal fusion peptide that initiates virus-cell membrane fusion. The fusion peptide is linked to the coiled-coil core through a conserved sequence that is often rich in glycines. We investigated the functional role of the glycine-rich segment, Met-326 to Ser-337, of the human T-cell leukemia virus type 1 (HTLV-1) TM, gp21, by alanine and proline scanning mutagenesis. Alanine substitution for the hydrophobic residue Ile-334 caused an ~90% reduction in cell-cell fusion activity without detectable effects on the lipid-mixing and pore formation phases of fusion. Alanine substitutions at other positions had smaller effects (Gly-329, Val-330, and Gly-332) or no effect on fusion function. Proline substitution for glycine residues inhibited cell-cell fusion function with position-dependent effects on the three phases of fusion. Retroviral glycoprotein fusion function thus appears to require flexibility within the glycine-rich segment and hydrophobic contacts mediated by this segment.

* Corresponding author. Present address: Macfarlane Burnet Institute for Medical Research and Public Health, G.P.O. Box 2284, Melbourne, Victoria 3001, Australia. Phone: 61-3-9282-2111. Fax: 61-3-9282-2100. E-mail: apoumbourios{at}burnet.edu.au.

{dagger} Present address: Biochemistry and Cell Biology, Rice University, Houston, Texas 77251-1892.

{ddagger} Present address: Department of Cell Biology, Institut Cochin, Paris 75014, France.

Journal of Virology, April 2005, p. 4533-4539, Vol. 79, No. 7
0022-538X/05/$08.00+0     doi:10.1128/JVI.79.7.4533-4539.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.





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