Membrane location and special properties of cluster N2 in complex I of Escherichia coli.

Format:

Book

Thesis/Dissertation

Author/Creator:

Hopper, Elizabeth Anne.

Contributor:

University of Pennsylvania.

Language:

English

Subjects (All):

Biophysics.

Biochemistry.

0487.

0786.

Local Subjects:

0487.

0786.

Physical Description:

133 pages

Contained In:

Dissertation Abstracts International 60-04B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

NADH-quinone oxidoreductase (complex I) is a membrane bound enzyme of the respiratory chain in mammalian mitochondria. It catalyzes electron transfer from NADH to the ubiquinone pool with concomitant vectorial proton translocation across the mitochondrial membrane. Complex I contains 6 EPR detectable iron-sulfur clusters, one flavin mononucleotide and at least two bound forms of ubiquinone.

The iron-sulfur cluster N2 is of particular interest because it has a redox midpoint potential (Em) which is at least 100 mV higher than other clusters in complex I, its apparent Em is pH dependent, and it is located within the cytoplasmic membrane surface. Therefore, N2 could be the direct electron donor to a bound form of quinone. It is likely that FMN and a chain of iron-sulfur clusters function as an electron guide from NADH to N2.

This dissertation describes a novel protocol that allows investigation of the iron-sulfur cluster N2 without EPR signal interference from other iron-sulfur clusters. In our membrane topology studies of complex I, it was found that the soluble portion of complex I can be removed without detergent simply by changing the pH of the membrane suspension from 6 to 9. The iron-sulfur cluster N2 remains in the membrane fraction, and all other iron-sulfur clusters are removed. The rare earth ion dysprosium was used in order to enhance EPR signals in this system by relieving microwave power saturation. The use of the paramagnetic probe dysprosium permits the estimation of distances in this systems, specifically the distance of N2 to the hydrophobic surface.

This dissertation will further provide some discussion of the unique properties of N2 observed in our system using the method of redox potentiometry.

Notes:

Source: Dissertation Abstracts International, Volume: 60-04, Section: B, page: 1476.

Adviser: Tomoko Ohnishi.

Thesis (Ph.D.)--University of Pennsylvania, 1999.

Local Notes:

School code: 0175.

ISBN:

9780599259034

Access Restriction:

Restricted for use by site license.