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In human cells, the best-characterized iron-sensing mechanism is the result of post-transcriptional regulation of mRNA (the chemical instructions derived from DNA genes to make proteins). Sequences of mRNA called iron-responsive elements (IREs) are contained within the mRNA sequences that code for transferrin receptors and for ferritin.
Serum iron is a medical laboratory test that measures the amount of circulating iron that is bound to transferrin and freely circulate in the blood. Clinicians order this laboratory test when they are concerned about iron deficiency, which can cause anemia and other problems. 65% of the iron in the body is bound up in hemoglobin molecules in red blood cells.
The amino acids which bind the iron ion to the transferrin are identical for both lobes; two tyrosines, one histidine, and one aspartic acid. For the iron ion to bind, an anion is required, preferably carbonate (CO 2− 3). [18] [13] Transferrin also has a transferrin iron-bound receptor; it is a disulfide-linked homodimer. [16]
It means that transferrin has the capacity to transport approximately from 1.40 to 1.49 mg of iron per gram of transferrin present in the blood. [ 2 ] It is performed by drawing blood and measuring the maximum amount of iron that it can carry, which indirectly measures transferrin [ 3 ] since transferrin is the most dynamic carrier.
The human diet contains iron in two forms: heme iron and non-heme iron. Heme iron is usually found in red meat, whereas non-heme iron is found in plant based sources. Heme iron is the most easily absorbed form of iron. In those with hemochromatosis undergoing phlebotomy for treatment; restriction of dietary iron is not required.
[3] [4] [10] In mammalian hosts, iron is tightly bound to proteins such as hemoglobin, transferrin, lactoferrin and ferritin. The strict homeostasis of iron leads to a free concentration of about 10 −24 mol L −1 , [ 11 ] hence there are great evolutionary pressures put on pathogenic bacteria to obtain this metal.
Iron tests are groups of clinical chemistry laboratory blood tests that are used to evaluate body iron stores or the iron level in blood serum. Other terms used for the same tests are iron panel , iron profile , iron indices , iron status or iron studies .
Iron bound to proteins or cofactors such as heme is safe. Also, there are virtually no truly free iron ions in the cell, since they readily form complexes with organic molecules. However, some of the intracellular iron is bound to low-affinity complexes, and is termed labile iron or "free" iron.