Date of Award:

5-1981

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Chemistry and Biochemistry

Advisor/Chair:

Thomas F. Emery

Abstract

The transport and intracellular distribution of iron in Ustilago sphaerogena via the native siderochrome ferrichrome A has been examined. Evidence is presented which suggests the involvement of deferriferrichrome in iron transport when the metal is supplied to the cell as ferrichrome A. This process requires both oxygen and ATP synthesis and may require a transmembrane electrochemical gradient. Once inside the cell, iron derived from ferrichrome A is rapidly distributed, with a major fraction found in the mitochondria, presumably as heme.

The kinetics of ferrichrome and ferrichrome A uptake have also been investigated. The Km of transport of ferrichrome was determined to be 0.6 μM with a maximum velocity of 1.55 nmoles/min/mg. For ferrichrome A the Km was found to be 7.6 μM; Vmax was 0.85 nmoles/ min/mg. Ferrichrome functions as a competitive inhibitor of ferrichrome A transport with a Ki of 14 μM, while ferrichrome A inhibited ferrichrome transport in a noncompetitive manner. Together these data are consistent with a two-site model for siderochrome transport. A model for the transport process is presented.

The exchange of iron from fcA to deferrifch has also been examined. The ratio of the binding constants between fcA and fch was found to be 5.29. From this data the binding constant for fcA was determined to be 6.82x10^29.

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