Only five of 10 strictly conserved disulfide bonds are essential for folding and eight for function of the HIV-1 envelope glycoprotein.
Protein folding in the endoplasmic reticulum goes hand in hand with disulfide bond formation, and disulfide bonds are considered key structural elements for a protein's folding and function. We used the HIV-1 Envelope glycoprotein to examine in detail the importance of its 10 completely conserved disulfide bonds. We systematically mutated the cysteines in its ectodomain, assayed the mutants for oxidative folding, transport, and incorporation into the virus, and tested fitness of mutant viruses. We found that the protein was remarkably tolerant toward manipulation of its disulfide-bonded structure. Five of 10 disulfide bonds were dispensable for folding. Two of these were even expendable for viral replication in cell culture, indicating that the relevance of these disulfide bonds becomes manifest only during natural infection. Our findings refine old paradigms on the importance of disulfide bonds for proteins.
van Anken
Eelco
E
Cellular Protein Chemistry, Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands.
Sanders
Rogier W
RW
Liscaljet
I Marije
IM
Land
Aafke
A
Bontjer
Ilja
I
Tillemans
Sonja
S
Nabatov
Alexey A
AA
Paxton
William A
WA
Berkhout
Ben
B
Braakman
Ineke
I
D000409:Alanine / Q000737:chemistry; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000737:chemistry*; D019302:HIV Envelope Protein gp160 / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010100:Oxygen / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport
D004220:Disulfides; D015699:HIV Envelope Protein gp120; D019302:HIV Envelope Protein gp160; D003545:Cysteine; D000409:Alanine; D010100:Oxygen