Iron storage in bacteria.

摘要: Iron is an essential nutrient for nearly all organisms but presents problems of toxicity, poor solubility and low availability. These are alleviated through the use iron-storage proteins. Bacteria possess two types protein, haem-containing bacterioferritins haem-free ferritins. proteins widespread in bacteria, with at least 39 examples known so far eubacteria archaebacteria. The ferritins distantly related retain similar structural functional properties. Both composed 24 identical or subunits (approximately 19 kDa) that form a roughly spherical protein 450 kDa, approximately 120 A diameter) containing large hollow centre 80 diameter). acts as cavity capacity to accommodate 2000 iron atoms ferric-hydroxyphosphate core. Each subunit contains four-helix bundle which carries active site ferroxidase protein. centres endow ferrous-iron-oxidizing activity able di-iron species intermediate uptake, oxidation core formation process. Bacterioferritins contain up 12 protoporphyrin IX haem groups located two-fold interfaces between pairs subunits. role unknown, although it may be involved mediating iron-core reduction release. Some types, one conferring haem-binding ability (alpha) other (beta) bestowing activity. Bacterioferritin genes often adjacent encoding small [2Fe-2S]-ferredoxin (bacterioferritin-associated ferredoxin Bfd). Bfd directly interact bacterioferritin could releasing from (or delivering to) complexes. bacteria subunits, ferritin most cases co-assemble. Others both ferritin, while some appear lack any type reason these differences not understood. Studies on mutants have shown enhances growth during starvation also accumulation stationary phase growth. Campylobacter jejuni redox stress resistance, this does case Escherichia coli (FtnA). No phenotype has been determined E. precise remains uncertain.