Abstract Hemoglobin III (HbIII) is one of the two oxygen reactive hemoproteins present in the bivalve,Lucina pectinata. The clam inhabits a sulfur‐rich environment and HbIII is the only hemoprotein present in the system which does not yet have a structure described elsewhere. It is known that HbIII exists as a heterodimer with hemoglobin II (HbII) to generate the stable Oxy(HbII‐HbIII) complex but it remains unknown if HbIII can form a homodimeric species. Here, a new chromatographic methodology to separate OxyHbIII from the HbII‐HbIII dimer has been developed, employing a fast performance liquid chromatography and ionic exchange chromatography column. The nature of OxyHbIII in solution at concentrations from 1.6 mg/mL to 20.4 mg/mL was studied using small angle X‐ray scattering (SAXS). The results show that at all concentrations, the Oxy(HbIII‐HbIII) dimer dominates in solution. However, as the concentration increases to nonphysiological values, 20.4 mg/mL, HbIII forms a 30% tetrameric fraction. Thus, there is a direct relationship between the Oxy(HbIII‐HbIII) oligomeric form and hemoglobin concentration. We suggest it is likely that the OxyHbIII dimer contributes to active oxygen transport in tissues ofL pectinata, where the Oxy(HbII‐HbIII) complex is not present.
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ClassicalGSG : Prediction of log P using classical molecular force fields and geometric scattering for graphs
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SUMMARY Carotenoids perform a broad range of important functions in humans; therefore, carotenoid biofortification of maize (Zea maysL.), one of the most highly produced cereal crops worldwide, would have a global impact on human health.PLASTID TERMINAL OXIDASE(PTOX) genes play an important role in carotenoid metabolism; however, the possible function ofPTOXin carotenoid biosynthesis in maize has not yet been explored. In this study, we characterized the maizePTOXlocus by forward‐ and reverse‐genetic analyses. While most higher plant species possess a single copy of thePTOXgene, maize carries two tandemly duplicated copies. Characterization of mutants revealed that disruption of either copy resulted in a carotenoid‐deficient phenotype. We identified mutations in thePTOXgenes as being causal of the classic maize mutant,albescent1. Remarkably, overexpression ofZmPTOX1significantly improved the content of carotenoids, especially β‐carotene (provitamin A), which was increased by ~threefold, in maize kernels. Overall, our study shows that maizePTOXlocus plays an important role in carotenoid biosynthesis in maize kernels and suggests that fine‐tuning the expression of this gene could improve the nutritional value of cereal grains.more » « less
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