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Enhanced internal dynamics of a membrane transport protein during substrate translocation

Published online by Cambridge University Press:  15 December 2000

KLAUS DÖRING ,
THOMAS SURREY ,
SYLVIA GRÜNEWALD ,
EDGAR JOHN  and
FRITZ JÄHNIG
KLAUS DÖRING
Affiliation:
Max-Planck-Institute for Biology, Department of Membrane Biochemistry, Corrensstrasse 38, 72076 Tübingen, Germany Present address: Tecan Austria Ges.m.b.H, Untersbergstrasse 1A, 5082 Grödig, Austria.
THOMAS SURREY
Affiliation:
Max-Planck-Institute for Biology, Department of Membrane Biochemistry, Corrensstrasse 38, 72076 Tübingen, Germany Present address: European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
SYLVIA GRÜNEWALD
Affiliation:
Max-Planck-Institute for Biology, Department of Membrane Biochemistry, Corrensstrasse 38, 72076 Tübingen, Germany Present address: BASF-LYNX Bioscience AG, Im Neuenheimer Feld 515, 69120 Heidelberg, Germany.
EDGAR JOHN
Affiliation:
Max-Planck-Institute for Biology, Department of Membrane Biochemistry, Corrensstrasse 38, 72076 Tübingen, Germany Present address: Novartis Pharma AG, K-127.3.32, 4002 Basel, Switzerland.
FRITZ JÄHNIG
Affiliation:
Max-Planck-Institute for Biology, Department of Membrane Biochemistry, Corrensstrasse 38, 72076 Tübingen, Germany
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Abstract

Conformational changes are essential for the activity of many proteins. If, or how fast, internal fluctuations are related to slow conformational changes that mediate protein function is not understood. In this study, we measure internal fluctuations of the transport protein lactose permease in the presence and absence of substrate by tryptophan fluorescence spectroscopy. We demonstrate that nanosecond fluctuations of α-helices are enhanced when the enzyme transports substrate. This correlates with previously published kinetic data from transport measurements showing that millisecond conformational transitions of the substrate-loaded carrier are faster than those in the absence of substrate. These findings corroborate the hypothesis of the hierarchical model of protein dynamics that predicts that slow conformational transitions are based on fast, thermally activated internal motions.

Keywords

helix fluctuationslactose permeasenanosecond motionsprotein dynamicstime-resolved tryptophan fluorescence anisotropy
Type
Research Article
Information
Protein Science , Volume 9 , Issue 11 , November 2000 , pp. 2246 - 2250
Copyright
2000 The Protein Society

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