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9 results on '"Avramov, Anton P."'

7. The role of Ca2+ and protein scaffolding in the formation of nature's water oxidizing complex.

Author

Avramov, Anton P., Hwang, Hong J., and Burnap, Robert L.

Subjects
*SCAFFOLD proteins, *PHOTOSYSTEMS, *QUANTUM efficiency, *NATURE, *REARRANGEMENTS (Chemistry)
Abstract

Photosynthetic O2 evolution is catalyzed by the Mn4CaO5 cluster of the water oxidation complex of the photosystem II (PSII) complex. The photooxidative self-assembly of the Mn4CaO5 cluster, termed photoactivation, utilizes the same highly oxidizing species that drive the water oxidation in order to drive the incorporation of Mn2+ into the high-valence Mn4CaO5 cluster. This multistep process proceeds with low quantum efficiency, involves a molecular rearrangement between light-activated steps, and is prone to photoinactivation and misassembly. A sensitive polarographic technique was used to track the assembly process under flash illumination as a function of the constituent Mn2+ and Ca2+ ions in genetically engineered membranes of the cyanobacterium Synechocystis sp. PCC6803 to elucidate the action of Ca2+ and peripheral proteins. We show that the protein scaffolding organizing this process is allosterically modulated by the assembly protein Psb27, which together with Ca2+ stabilizes the intermediates of photoactivation, a feature especially evident at long intervals between photoactivating flashes. The results indicate three critical metalbinding sites: two Mn and one Ca, with occupation of the Ca site by Ca2+ critical for the suppression of photoinactivation. The longobserved competition between Mn2+ and Ca2+ occurs at the second Mn site, and its occupation by competing Ca2+ slows the rearrangement. The relatively low overall quantum efficiency of photoactivation is explained by the requirement of correct occupancy of these metal-binding sites coupled to a slow restructuring of the protein ligation environment, which are jointly necessary for the photooxidative trapping of the first stable assembly intermediate. [ABSTRACT FROM AUTHOR]

Published
2020
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8. Content of Metals in Phragmites australis Trin. ex Steud and Potamogeton pectinatus L. from Water Bodies of Different Salinity

Author

Ivanova, Elena A., Anishchenko, Olesya V., Zuev, Ivan V., and Avramov, Anton P.

Subjects
макроэлементы, macroelements, reservoir, макрофиты, солоноватоводные озера, microelements, микроэлементы, metals, металлы, минерализация, водохранилище, brackish lake, salinity, macrophytes
Abstract

Металлы определяли в двух видах макрофитов – Phragmites australis Trin. ex Steud и Potamogeton pectinatus L., произрастающих в водоемах с разной соленостью, с помощью эмиссионного спектрометра с индуктивно-связанной плазмой. Анализ результатов методом главных компонент показал, что на валовое содержание металлов влияет вид макрофитов и условия окружающей среды, в частности химический состав воды. Оба вида макрофитов из пресноводного водохранилища Бугач отличались более высокими концентрациями железа, алюминия, никеля, ванадия и кобальта по сравнению с теми же видами макрофитов, собранными в солоноватоводных озерах. Однако для макрофитов из оз. Шира, отобранных в опресненной и солоноватоводной частях озера, расхождений в содержании данных металлов не выявлено. В ряде случаев пробы из одной точки, но собранные в разные годы имели существенные различия – это наблюдалось для растений тростника из солоноватоводной станции оз. Шира, и растений рдеста из оз. Шунет. Было установлено, что наиболее высокое валовое содержание большинства металлов характерно для P. pectinatus Metals were determined in two species of macrophytes Phragmites australis Trin. ex Steud and Potamogeton pectinatus L. grown in lakes of different salinity, using emission spectrometer with inductively coupled plasma. Principal component analysis revealed that the total metal content is influenced by species of macrophytes and environmental conditions (in particular water chemistry). Both species of macrophytes from freshwater reservoir Bugach were characterized by higher concentrations of Fe, Al, Ni, V and Co in comparison with the same species from brackish lakes. However, there were no significant differences in content of these metals between samples of macrophytes taken in desalinated and saltwater parts of Shira Lake. In some cases, metal content of samples collected in different years at the same place were significantly different. It was observed for plants of Ph. australis collected in brackish station of Shira Lake, and plants of P. pectinatus from Lake Shunet. It was found that the highest total content of most metals is typical for P. pectinatus

Published
2015

9. Draft genome sequence of Microbacterium oleivoransstrain Wellendorf implicates heterotrophic versatility and bioremediation potential

Author

Avramov, Anton P., Couger, M.B., Hartley, Emily L., Land, Craig, Wellendorf, Rachel, Hanafy, Radwa A., Budd, Connie, French, Donald P., Hoff, Wouter D., and Youssef, Noha

Abstract

Microbacterium oleivoransis a predominant member of hydrocarbon-contaminated environments. We here report on the genomic analysis of M. oleivoransstrain Wellendorf that was isolated from an indoor door handle. The partial genome of M. oleivoransstrain Wellendorf consists of 2,916,870bp of DNA with 2831 protein-coding genes and 49 RNA genes. The organism appears to be a versatile mesophilic heterotroph potentially capable of hydrolysis a suite of carbohydrates and amino acids. Genomic analysis revealed metabolic versatility with genes involved in the metabolism and transport of glucose, fructose, rhamnose, galactose, xylose, arabinose, alanine, aspartate, asparagine, glutamate, serine, glycine, threonine and cysteine. This is the first detailed analysis of a Microbacterium oleivoransgenome.

Published
2016
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