Electrostatic redesign of the [Myoglobin, Cytochrome b 5] interface to create a well-defined docked complex with rapid Lnterprotein electron transfer

Peng Xiong, Judith M. Nocek, Amanda K.K. Griffin, Jingyun Wang, Brian M. Hoffman

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Cyt b 5 is the electron-carrier "repair" protein that reduces met-Mb and met-Hb to their O 2-carrying ferroheme forms. Studies of electron transfer (ET) between Mb and cyt b 5 revealed that they react on a "Dynamic Docking" (DD) energy landscape on which binding and reactivity are uncoupled: binding is weak and involves an ensemble of nearly isoenergetic configurations, only a few of which are reactive; those few contribute negligibly to binding. We set the task of redesigning the surface of Mb so that its reaction with cyt b5 instead would occur on a conventional "simple docking" (SD) energy landscape, on which a complex exhibits a well-defined (set of) reactive binding configuration(s), with binding and reactivity thus no longer being decoupled. We prepared a myoglobin (Mb) triple mutant (D44K/D60K/E85K; Mb(+6)) substituted with Zn-deuteroporphyrin and monitored cytochrome b 5 (cyt b 5) binding and electron transfer (ET) quenching of the 3ZnMb(+6) triplet state. In contrast, to Mb(WT), the three charge reversals around the "front-face" heme edge of Mb(+6) have directed cyt b5 to a surface area of Mb adjacent to its heme, created a well-defined, most-stable structure that supports good ET pathways, and apparently coupled binding and ET: both Ka and ket are increased by the same factor of 2 × 102, creating a complex that exhibits a large ET rate constant, k et = 10 6 1s -1, and is in slow exchange (k off « k et). In short, these mutations indeed appear to have created the sought-for conversion from DD to simple docking (SD) energy landscapes.

Original languageEnglish (US)
Pages (from-to)6938-6939
Number of pages2
JournalJournal of the American Chemical Society
Volume131
Issue number20
DOIs
StatePublished - May 27 2009

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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