Do Protein Molecules Have a Native-Like Topology in the Pre-molten Globule State?

V. N. Uversky^1* and A. L. Fink²

¹Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (095) 924-0493; E-mail: uversky@vega.protres.ru

²Department of Chemistry, University of California Santa Cruz, CA 95064, USA

^* To whom correspondence should be addressed.

Received May 18, 1998; Revision received December 4, 1998

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The process of anion-induced refolding of acid unfolded apomyoglobin with a modified tyrosine residue (Tyr-146(NO₂)) has been characterized by intrinsic protein fluorescence. It is shown that under conditions inducing the protein molecule transition into the pre-molten globule state (i.e., at low pH (2.5) and increased sulfate concentration) there is a significant quenching of the tryptophan fluorescence of the protein resulting from efficient energy transfer from the tryptophan residues to the nitrotyrosine residue. This may mean that the protein molecule in the pre-molten globule state has a native-like topology.

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KEY WORDS: pre-molten globule state, anion-induced folding, energy transfer, nitrotyrosine

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