Interrelationship between cytoplasmic retroviral Gag concentration and Gag-membrane association

Keir H. Fogarty, Serkan Berk, Iwen F. Grigsby, Yan Chen, Louis M. Mansky, Joachim D. Mueller

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The early events in the retrovirus assembly pathway, particularly the timing and nature of Gag translocation from the site of protein translation to the inner leaflet of the plasma membrane, are poorly understood. We have investigated the interrelationship between cytoplasmic Gag concentration and plasma membrane association using complementary live-cell biophysical fluorescence techniques in real time with both human T-cell leukemia virus type 1 (HTLV-1) and human immunodeficiency virus type 1 (HIV-1) Gag proteins. In particular, dual-color, z-scan fluorescence fluctuation spectroscopy in conjunction with total internal reflection fluorescence and conventional, epi-illumination imaging were utilized. Our results demonstrate that HTLV-1 Gag is capable of membrane targeting and particle assembly at low (i.e., nanomolar) cytoplasmic concentrations and that there is a critical threshold concentration (approaching micromolar) prior to the observation of HIV-1 Gag associated with the plasma membrane. These observations imply fundamental differences between HIV-1 and HTLV-1 Gag trafficking and membrane association.

Original languageEnglish (US)
Pages (from-to)1611-1624
Number of pages14
JournalJournal of Molecular Biology
Issue number7
StatePublished - Apr 3 2014

Bibliographical note

Funding Information:
This research was supported by National Institutes of Health grants R01GM098550 and R01GM064589 and the National Science Foundation ( PHY-0346782 ). K.H.F. was supported from an American Cancer Society Postdoctoral Fellowship.


  • assembly
  • fluorescence
  • membrane
  • oligomerization
  • retrovirus


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