Maricaulis maris MCS10
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA17333 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| GCA_000014745.1_sequence_report.txt | Txt |
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Project description:Maricaulis maris N-acetylglutamate synthase/kinase (mmNAGS/K) catalyzes the first two steps in L-arginine biosynthesis and has a high degree of sequence and structural homology to human N-acetylglutamate synthase, a regulator of the urea cycle. The synthase activity of both mmNAGS/K and human NAGS are regulated by L-arginine, although L-arginine is an allosteric inhibitor of mmNAGS/K, but an activator of human NAGS. To investigate the mechanism of allosteric inhibition of mmNAGS/K by L-arginine, we have determined the structure of the mmNAGS/K complexed with L-arginine at 2.8 Å resolution. In contrast to the structure of mmNAGS/K in the absence of L-arginine where there are conformational differences between the four subunits in the asymmetric unit, all four subunits in the L-arginine liganded structure have very similar conformations. In this conformation, the AcCoA binding site in the N-acetyltransferase (NAT) domain is blocked by a loop from the amino acid kinase (AAK) domain, as a result of a domain rotation that occurs when L-arginine binds. This structural change provides an explanation for the allosteric inhibition of mmNAGS/K and related enzymes by L-arginine. The allosterically regulated mechanism for mmNAGS/K differs significantly from that for Neisseria gonorrhoeae NAGS (ngNAGS). To define the active site, several residues near the putative active site were mutated and their activities determined. These experiments identify roles for Lys356, Arg386, Asn391 and Tyr397 in the catalytic mechanism.
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Project description:Novel bifunctional N-acetylglutamate synthase/kinases (NAGS/K) that catalyze the first two steps of arginine biosynthesis and are homologous to vertebrate N-acetylglutamate synthase (NAGS), an essential cofactor-producing enzyme in the urea cycle, were identified in Maricaulis maris and several other bacteria. Arginine is an allosteric inhibitor of NAGS but not NAGK activity. The crystal structure of M. maris NAGS/K (mmNAGS/K) at 2.7 Å resolution indicates that it is a tetramer, in contrast to the hexameric structure of Neisseria gonorrhoeae NAGS. The quaternary structure of crystalline NAGS/K from Xanthomonas campestris (xcNAGS/K) is similar, and cross-linking experiments indicate that both mmNAGS/K and xcNAGS are tetramers in solution. Each subunit has an amino acid kinase (AAK) domain, which is likely responsible for N-acetylglutamate kinase (NAGK) activity and has a putative arginine binding site, and an N-acetyltransferase (NAT) domain that contains the putative NAGS active site. These structures and sequence comparisons suggest that the linker residue 291 may determine whether arginine acts as an allosteric inhibitor or activator in homologous enzymes in microorganisms and vertebrates. In addition, the angle of rotation between AAK and NAT domains varies among crystal forms and subunits within the tetramer. A rotation of 26° is sufficient to close the predicted AcCoA binding site, thus reducing enzymatic activity. Since mmNAGS/K has the highest degree of sequence homology to vertebrate NAGS of NAGS and NAGK enzymes whose structures have been determined, the mmNAGS/K structure was used to develop a structural model of human NAGS that is fully consistent with the functional effects of the 14 missense mutations that were identified in NAGS-deficient patients.
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Project description:In the mouse neocortex, neural progenitor cells generate neurons through repeated rounds of asymmetric cell division. How distinct fates are established in their daughter cells is unclear. We show here that the TRIM-NHL protein TRIM32 segregates asymmetrically during progenitor division and induces neuronal differentiation in one of the two daughter cells. TRIM32 is highly expressed in differentiating neurons. In both horizontally and vertically dividing progenitor cells, TRIM32 distribution becomes polarized in mitosis so that the protein is enriched in one of the two daughter cells. While TRIM32 overexpression induces cell cycle exit and neuronal differentiation, TRIM32 RNAi causes both daughter cells to proliferate and prevents the initiation of a neuronal differentiation program . TRIM32 ubiquitinates and degrades the transcription factor c-Myc but also binds Argonaute-1 and thereby increases the activity of specific micro-RNAs. We show that Let-7 is one of the TRIM32 targets and is required and sufficient for neuronal differentiation. Our data suggest that the asymmetric segregation of a micro RNA regulator controls self renewal in the mammalian brain. Experiment Overall Design: small RNA from total mouse brain, Ago-1 and TRIM32 IPs were cloned and sequenced using 454 GS FLX system.
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Project description:Asymmetric partitioning of fate-determinants is a mechanism that contributes to T cell differentiation. However, it remained unclear whether the ability of T cells to divide asymmetrically is influenced by their differentiation state, as well as if enforcing asymmetric cell division rates would have an impact on T cell differentiation and memory formation. Using the murine LCMV infection model, we established a correlation between cell stemness and the ability of CD8+ T cells to undergo asymmetric cell division (ACD). Transient mTOR inhibition proved to increase ACD rates in naïve and memory cells, and to install this ability in exhausted CD8+ T cells. Functionally, enforced ACD correlated with increased memory potential, leading to more efficient recall response and viral control upon acute or chronic LCMV infection. Moreover, transient mTOR inhibition also increased ACD rates in human CD8+ T cells. Transcriptional profiling of first daughter cells, obtained by sorting CD8lo and CD8hi cells after in vitro stimulation, revealed that progenies emerging from enforced ACD exhibited more pronounced early memory signatures, which functionally endowed these cells with strengthened memory features.
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