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Structural rearrangement of human lymphotactin, a C chemokine, under physiological solution conditions. J Biol Chem 2002 May 17;277(20):17863-70

Date

03/13/2002

Pubmed ID

11889129

Pubmed Central ID

PMC4451178

DOI

10.1074/jbc.M200402200

Scopus ID

2-s2.0-0037124112   47 Citations

Abstract

NMR spectra of human lymphotactin (hLtn), obtained under various solution conditions, have revealed that the protein undergoes a major conformational rearrangement dependent on temperature and salt concentration. At high salt (200 mm NaCl) and low temperature (10 degrees C), hLtn adopts a chemokine-like fold, which consists of a three-stranded antiparallel beta-sheet and a C-terminal alpha-helix (Kuloğlu, E. S., McCaslin, D. R., Kitabwalla, M., Pauza, C. D., Markley, J. L., and Volkman, B. F. (2001) Biochemistry 40, 12486-12496). We have used NMR spectroscopy, sedimentation equilibrium, and intrinsic fluorescence to monitor the reversible conformational change undergone by hLtn as a function of temperature and ionic strength. We have used two-, three- and four-dimensional NMR spectroscopy of isotopically enriched protein samples to determine structural properties of the conformational state stabilized at 45 degrees C and 0 mm NaCl. Patterns of NOEs and (1)H(alpha) and (13)C chemical shifts show that hLtn rearranges under these conditions to form a four-stranded, antiparallel beta-sheet with a pattern of hydrogen bonding that is completely different from that of the chemokine fold stabilized at 10 degrees C and 200 mm NaCl. The C-terminal alpha-helix observed at 10 degrees C and 200 mm NaCl, which is conserved in other chemokines, is absent at 45 degrees C and no salt, and the last 38 residues of the protein are completely disordered, as indicated by heteronuclear (15)N-(1)H NOEs. Temperature dependence of the tryptophan fluorescence of hLtn in low and high salt confirmed that the chemokine conformation is stabilized by increased ionic strength. Sedimentation equilibrium analytical ultracentrifugation showed that hLtn at 40 degrees C in the presence of 100 mm NaCl exists mainly as a dimer. Under near physiological conditions of temperature, pH, and ionic strength, both the chemokine-like and non-chemokine-like conformations of hLtn are significantly populated. The functional relevance of this structural interconversion remains to be elucidated.

Author List

Kuloğlu ES, McCaslin DR, Markley JL, Volkman BF

Author

Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Chemokines, C
Humans
Hydrogen-Ion Concentration
Lymphokines
Magnetic Resonance Spectroscopy
Protein Conformation
Protein Structure, Secondary
Sialoglycoproteins
Sodium Chloride
Spectrometry, Fluorescence
Temperature
Ultracentrifugation
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