In most free-living eukaryotes studied thus far, heme is synthesized from a series of intermediates through a well defined evolutionarily conserved pathway. We found that free-living worms, including the model genetic organism Caenorhabditis elegans, and parasitic helminths are unable to synthesize heme de novo, even though these animals contain hemoproteins that function in key biological proc...

Bartonellae are hemotropic bacteria, agents of emerging zoonoses. These bacteria are heme auxotroph Alphaproteobacteria which must import heme for supporting their growth, as they cannot synthesize it. Therefore, Bartonella genome encodes for a complete heme uptake system allowing the transportation of this compound across the outer membrane, the periplasm and the inner membranes. Heme has been...

UNLABELLED The protein YfeX from Escherichia coli has been proposed to be essential for the process of iron removal from heme by carrying out a dechelation of heme without cleavage of the porphyrin macrocycle. Since this proposed reaction is unique and would represent the first instance of the biological dechelation of heme, we undertook to characterize YfeX. Our data reveal that YfeX effective...

Bacteria that reside in animal tissues and/or cells must acquire iron from their host. However, almost all of the host iron is sequestered in iron-containing compounds and proteins, the majority of which is found within heme molecules. Thus, likely iron sources for bacterial pathogens (and non-pathogenic symbionts) are free heme and heme-containing proteins. Furthermore, the cellular location o...

In most organisms, heme biosynthesis is strictly controlled so as to avoid heme and heme precursor accumulation, which is toxic. Escherichia coli regulates heme biosynthesis by a feedback loop involving heme-induced proteolytic cleavage of HemA, glutamyl-tRNA reductase, which is the first enzyme in the heme biosynthetic pathway. We show here that heme homeostasis can be disrupted by overproduct...

Heme-regulated eIF2alpha kinase (HRI) is essential for regulating globin translation in iron deficiency and in beta-thalassemia. We investigated the role of heme-regulated eIF2alpha kinase in hemoglobin and red blood cell production as well as in iron homeostasis in a mouse model of iron overload. We show that HRI deficiency does not significantly affect red cell parameters of hemochromatosis (...

For over 100 years it has been known that iron is essential for the growth of higher plants and that it is involved in some manner with chlorophyll metabolism. Jljin (17, 18, 19) demonstrated that iron deficiency in plants resulted in decreased dry weight, salt, and protein nitrogen contents and increased contents of amino and organic acids. Extensive studies (8, 9, 25, 33) have confirmled Ilj ...

S. aureus is a pathogenic bacterium that requires iron to carry out vital metabolic functions and cause disease. The most abundant reservoir of iron inside the human host is heme, which is the cofactor of hemoglobin. To acquire iron from hemoglobin, S. aureus utilizes an elaborate system known as the iron-regulated surface determinant (Isd) system. Components of the Isd system first bind host h...

The objective of this study was to assess the association of markers in the calpastatin and mu-calpain loci with iron in beef cattle muscle. The population consisted of 259 cross-bred steers from Beefmaster, Brangus, Bonsmara, Romosinuano, Hereford and Angus sires. Total iron and heme iron concentrations were measured. Markers in the calpastatin (referred to as CAST) and mu-calpain (referred to...

The bacterium Sinorhizobium meliloti is able to use heme as a nutritional iron source. Here, we show that the iron-regulated shmR gene encodes an outer membrane protein required for growth on heme. Furthermore, an shmR mutant is resistant to the toxic heme analog gallium protoporphyrin. Thus, the receptor protein of the heme transport system has been identified in S. meliloti.