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Amit Ghosh

Bio: Amit Ghosh is an academic researcher from University of Calcutta. The author has contributed to research in topics: Oxygen binding & Leghemoglobin. The author has an hindex of 2, co-authored 3 publications receiving 26 citations.

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TL;DR: It is shown that due to the site-specific Lys to Ala mutations of PIP5K at Lys-244 and Lys-490, it is unable to localize in the nucleus and nucleolus, respectively, and it functions as a member of the rDNA silencing complex.

28 citations

Journal ArticleDOI
TL;DR: In vitro serine phosphorylation of recombinant LegH by a homologous kinase caused a reduction in its oxygen consumption as determined by Clark type electrode, and molecular modeling study showed that particularly S45 is the most critical one, along with S55, however the latter with lesser impact on its molecular environment responsible for oxygen consumption.
Abstract: In leguminous plants, nitrogenase that catalyzes anaerobic symbiotic nitrogen fixation is protected by the sequestration of O2 by Leghemoglobin (LegH). The modulation of the oxygen binding capacity of Hemoglobin (Hb) by different post-translational modifications is well studied; whereas similar studies on LegH’s O2 binding are not yet benchmarked. Our results show that in vitro serine phosphorylation of recombinant LegH from Lotus japonicus, a model legume, by a homologous kinase caused a reduction in its oxygen consumption as determined by Clark type electrode. Although mass spectrometry revealed a few phosphorylated serine residues in the LegH, molecular modeling study showed that particularly S45 is the most critical one, along with S55, however the latter with lesser impact on its molecular environment responsible for oxygen consumption. Separate S45D and S55D mutants of recombinant LegH also corroborated the results obtained from molecular modeling study. Thus, this work lays groundwork for further investigation of structural and functional role of serine phosphorylation as one of the mechanisms by which oxygen consumption by LegH may possibly be regulated during nodulation.

4 citations

Journal ArticleDOI
TL;DR: It is demonstrated that LegH interact in vitro with Nodulin 16 of Lotus japonicus (Nlj16), another late nodulin, which resulted in a bigger sized particle which shows higher diffusion coefficient and in vitro oxygen sequestration by LegH is stimulated by this interaction.
Abstract: Nodulin proteins are expressed in legume root cells after infection with rhizobia. Nodulins have been classified as early and late, reflecting the developmental time points of their expression. Leghemoglobin (LegH), which is a classical example of a late nodulin, sequesters oxygen inside the nodule to protect the nitrogenase from oxygen toxicity to sustain symbiotic nitrogen fixation (SNF). Post-translational modification and/or protein–protein interaction are known to regulate activity of proteins. To elucidate the role of post-translational modification of LegH on its oxygen sequestration activity, earlier we have shown that phosphorylation at its S45 imparts most structural disruption of the porphyrin binding pocket responsible for its oxygen binding. In the present report, in an attempt to characterize the protein(s) that may interact with LegH to regulate its activity, it is demonstrated that LegH interact in vitro with Nodulin 16 of Lotus japonicus (Nlj16), another late nodulin. These two interacting proteins resulted in a bigger sized particle which shows higher diffusion coefficient as measured by dynamic light scattering. Interestingly, it was also shown that in vitro oxygen sequestration by LegH is stimulated by this interaction. Furthermore, this interaction is validated by the fact that LegH and Nlj16 could be co-immunoprecipitated from the nodule lysate. Most importantly, fluorescent immunohistochemistry of post-infected nodule sections show perceivable co-localization of these two proteins in the nodule symbiosomes. Thus, this work is a foundation for further investigation on these two interacting late nodulins as one of the plausible regulations for the oxygen sequestration by LegH during SNF.

2 citations


Cited by
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Journal ArticleDOI
TL;DR: It is shown that IGS transcripts are required for establishing and maintaining a specific heterochromatic configuration at the promoter of a subset of rDNA arrays.
Abstract: Transcripts originating from the intergenic spacer (IGS) that separates rRNA genes (rDNA) have been known for two decades; their biological role, however, is largely unknown. Here we show that IGS transcripts are required for establishing and maintaining a specific heterochromatic configuration at the promoter of a subset of rDNA arrays. The mechanism of action appears to be mediated through the interaction of TIP5, the large subunit of the chromatin remodeling complex NoRC, with 150-300 nucleotide RNAs that are complementary in sequence to the rDNA promoter. Mutations that abrogate RNA binding of TIP5 impair the association of NoRC with rDNA and fail to promote H3K9&H4K20 methylation and HP1 recruitment. Knockdown of IGS transcripts abolishes the nucleolar localization of NoRC, decreases DNA methylation, and enhances rDNA transcription. The results reveal an important contribution of processed IGS transcripts in chromatin structure and epigenetic control of the rDNA locus.

117 citations

Journal ArticleDOI
TL;DR: A quantitative proteomic atlas of the model legume Medicago truncatula and its rhizobial symbiont Sinorhizobium meliloti is described, which includes more than 23,000 proteins, 20,000 phosphorylation sites, and 700 lysine acetylation sites, which provides insight into mechanisms regulating symbiosis.
Abstract: Legumes are essential components of agricultural systems because they enrich the soil in nitrogen and require little environmentally deleterious fertilizers. A complex symbiotic association between legumes and nitrogen-fixing soil bacteria called rhizobia culminates in the development of root nodules, where rhizobia fix atmospheric nitrogen and transfer it to their plant host. Here we describe a quantitative proteomic atlas of the model legume Medicago truncatula and its rhizobial symbiont Sinorhizobium meliloti, which includes more than 23,000 proteins, 20,000 phosphorylation sites, and 700 lysine acetylation sites. Our analysis provides insight into mechanisms regulating symbiosis. We identify a calmodulin-binding protein as a key regulator in the host and assign putative roles and targets to host factors (bioactive peptides) that control gene expression in the symbiont. Further mining of this proteomic resource may enable engineering of crops and their microbial partners to increase agricultural productivity and sustainability.

83 citations

Journal ArticleDOI
TL;DR: The tremendous progress made in research methods and advances in research techniques will make it possible to rationally control the diverse PTMs of heme proteins, especially those associated with human diseases, toward the authors' desired goals for a better life.

48 citations

Journal ArticleDOI
TL;DR: HowPPIns in the nucleus are modulated in response to external cues and how they function to control downstream signalling are discussed and a role for nuclear PPIns in liquid phase separations that are involved in the formation of membraneless compartments within the nucleus is suggested.
Abstract: Polyphosphoinositides (PPIns) are a family of seven lipid messengers that regulate a vast array of signalling pathways to control cell proliferation, migration, survival and differentiation. PPIns are differentially present in various sub-cellular compartments and, through the recruitment and regulation of specific proteins, are key regulators of compartment identity and function. Phosphoinositides and the enzymes that synthesise and degrade them are also present in the nuclear membrane and in nuclear membraneless compartments such as nuclear speckles. Here we discuss how PPIns in the nucleus are modulated in response to external cues and how they function to control downstream signalling. Finally we suggest a role for nuclear PPIns in liquid phase separations that are involved in the formation of membraneless compartments within the nucleus.

45 citations