Self-association of class I major histocompatibility complex molecules in liposome and cell surface membranes

Abhijit Chakrabarti, J. Matkó, Noorul A. Rahman, B. George Barisas, Michael Edidin

Research output: Contribution to journalArticle

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Abstract

Fluorescent derivatives of a human MHC class I glycoprotein, HLA-A2, were reconstituted into dimyristoylphosphatidylcholine (DMPC) liposomes. Measurements of lateral diffusion of fluorescein-(Fl-) labeled HLA-A2 by fluorescence photobleaching recovery (FPR), of rotational diffusion of erythrosin-(Er-) labeled HLA-A2 by time-resolved phosphorescence anisotropy (TPA), and of molecular proximity by flow cytometric fluorescence resonance energy transfer (FCET) showed that these class I MHC molecules self-associate in liposome membranes, forming small aggregates even at low surface concentrations. The lateral diffusion coefficient (Dlat) of Fl-HLA-A2 decreases with increasing surface protein concentration over a range of lipid:protein molar ratios (L/P) between 8000:1 and 2000:1. The reduction in Dlat of HLA molecules in DMPC liposomes is found to be sensitive to time and temperature. The rotational correlation time for Er-HLA-A2 in DMPC liposomes at 30 °C is 87 ± 0.8 μs, at least 10 times larger than that expected for an HLA monomer. There is also significant quenching of donor (Fl-HLA) fluorescence at 37 °C in the presence of acceptor-labeled (sulforhodamine-labeled HLA) protein indicating proximity between HLA molecules even at L/P = 4000:1. FPR and FCET measurements with another membrane glycoprotein, glycophorin, give no evidence for its self-association. HLA aggregation measured by FPR, FCET, and TPA was blocked by β2-microglobulin, b2m, added to the liposomes. The aggregation of HLA-A2 molecules is not an artifact of their reconstitution into liposomes. HLA aggregates, defined by FCET, were readily detected on the surface of human lymphoblastoid (JY) cells. These cells are known to display some class I HLA molecules lacking b2m.

Original languageEnglish
Pages (from-to)7182-7189
Number of pages8
JournalBiochemistry
Volume31
Issue number31
Publication statusPublished - 1992

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HLA-A2 Antigen
Major Histocompatibility Complex
Liposomes
Fluorescence Resonance Energy Transfer
Cell Membrane
Association reactions
Fluorescence Recovery After Photobleaching
Dimyristoylphosphatidylcholine
Membranes
Photobleaching
Molecules
Fluorescence
Phosphorescence
Anisotropy
Recovery
Agglomeration
Erythrosine
Glycophorin
Membrane Glycoproteins
Fluorescein

ASJC Scopus subject areas

  • Biochemistry

Cite this

Chakrabarti, A., Matkó, J., Rahman, N. A., Barisas, B. G., & Edidin, M. (1992). Self-association of class I major histocompatibility complex molecules in liposome and cell surface membranes. Biochemistry, 31(31), 7182-7189.

Self-association of class I major histocompatibility complex molecules in liposome and cell surface membranes. / Chakrabarti, Abhijit; Matkó, J.; Rahman, Noorul A.; Barisas, B. George; Edidin, Michael.

In: Biochemistry, Vol. 31, No. 31, 1992, p. 7182-7189.

Research output: Contribution to journalArticle

Chakrabarti, A, Matkó, J, Rahman, NA, Barisas, BG & Edidin, M 1992, 'Self-association of class I major histocompatibility complex molecules in liposome and cell surface membranes', Biochemistry, vol. 31, no. 31, pp. 7182-7189.
Chakrabarti, Abhijit ; Matkó, J. ; Rahman, Noorul A. ; Barisas, B. George ; Edidin, Michael. / Self-association of class I major histocompatibility complex molecules in liposome and cell surface membranes. In: Biochemistry. 1992 ; Vol. 31, No. 31. pp. 7182-7189.
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