“…It was previously shown that RrA can inhibit telomerase in cancer cells and normal human lymphocytes by inhibiting the expression of its catalytic subunit hTERT (human telomerase reverse transcriptase) [ 10 , 11 ]. We checked whether other L-ASNases have similar effects on telomerase by incubating Jurkat cells with enzymes of different origins.…”
Section: Resultsmentioning
confidence: 99%
“…Unfortunately, a NoLS motif has not been detected in the RrA sequence. It has already been established that NLSs often function NoLSs and accumulate proteins inside the nucleolus [ 10 ]. We predicted two NLS motifs located at the N- and C-terminus of the RrA polypeptide chain.…”
Section: Discussionmentioning
confidence: 99%
“…A very surprising cytotoxic asparagine-independent mechanism was described for a Rhodospirillum rubrum mutant L-ASNase with E149R, V150P, and F151T amino acid substitutions (RrA). RrA demonstrated regulatory capacity and could suppress telomerase activity in a number of human cancer cell lines, normal activated CD4 + T lymphocytes and xenografts of human solid tumors [ 10 , 11 ]. The role of RrA in telomerase suppression indirectly indicates its intracellular or even intranuclear localization as well as its ability to penetrate into the cellular membrane.…”
The anticancer effect of L-asparaginases (L-ASNases) is attributable to their ability to hydrolyze L-asparagine in the bloodstream and cancer cell microenvironment. Rhodospirillum rubrum (RrA) has dual mechanism of action and plays a role in the suppression of telomerase activity. The aim of this work was to investigate the possible mechanism of RrA penetration into human cancer cells. Labeling of widely used L-ASNases by fluorescein isothiocyanate followed by flow cytometry and fluorescent microscopy demonstrated that only RrA can interact with cell membranes. The screening of inhibitors of receptor-mediated endocytosis demonstrated the involvement of clathrin receptors in RrA penetration into cells. Confocal microscopy confirmed the cytoplasmic and nuclear localization of RrA in human breast cancer SKBR3 cells. Two predicted nuclear localization motifs allow RrA to penetrate into the cell nucleus and inhibit telomerase. Chromatin relaxation promoted by different agents can increase the ability of RrA to suppress the expression of telomerase main catalytic subunit. Our study demonstrated for the first time the ability of RrA to penetrate into human cancer cells and the involvement of clathrin receptors in this process.
“…It was previously shown that RrA can inhibit telomerase in cancer cells and normal human lymphocytes by inhibiting the expression of its catalytic subunit hTERT (human telomerase reverse transcriptase) [ 10 , 11 ]. We checked whether other L-ASNases have similar effects on telomerase by incubating Jurkat cells with enzymes of different origins.…”
Section: Resultsmentioning
confidence: 99%
“…Unfortunately, a NoLS motif has not been detected in the RrA sequence. It has already been established that NLSs often function NoLSs and accumulate proteins inside the nucleolus [ 10 ]. We predicted two NLS motifs located at the N- and C-terminus of the RrA polypeptide chain.…”
Section: Discussionmentioning
confidence: 99%
“…A very surprising cytotoxic asparagine-independent mechanism was described for a Rhodospirillum rubrum mutant L-ASNase with E149R, V150P, and F151T amino acid substitutions (RrA). RrA demonstrated regulatory capacity and could suppress telomerase activity in a number of human cancer cell lines, normal activated CD4 + T lymphocytes and xenografts of human solid tumors [ 10 , 11 ]. The role of RrA in telomerase suppression indirectly indicates its intracellular or even intranuclear localization as well as its ability to penetrate into the cellular membrane.…”
The anticancer effect of L-asparaginases (L-ASNases) is attributable to their ability to hydrolyze L-asparagine in the bloodstream and cancer cell microenvironment. Rhodospirillum rubrum (RrA) has dual mechanism of action and plays a role in the suppression of telomerase activity. The aim of this work was to investigate the possible mechanism of RrA penetration into human cancer cells. Labeling of widely used L-ASNases by fluorescein isothiocyanate followed by flow cytometry and fluorescent microscopy demonstrated that only RrA can interact with cell membranes. The screening of inhibitors of receptor-mediated endocytosis demonstrated the involvement of clathrin receptors in RrA penetration into cells. Confocal microscopy confirmed the cytoplasmic and nuclear localization of RrA in human breast cancer SKBR3 cells. Two predicted nuclear localization motifs allow RrA to penetrate into the cell nucleus and inhibit telomerase. Chromatin relaxation promoted by different agents can increase the ability of RrA to suppress the expression of telomerase main catalytic subunit. Our study demonstrated for the first time the ability of RrA to penetrate into human cancer cells and the involvement of clathrin receptors in this process.
“…activity in vivo [14][15][16][17][18]. RrA subunit has small molecular weight (18 kDa; monomer contains 172 amino acids).…”
Section: S3mentioning
confidence: 99%
“…KVS NIMA LB through), spreading 100 µm of protein solution with Hamilton syringe and compressing protein monolayer to a surface pressure of 20 mN/m by means of a Langmuir-Blodgett teflon barriers [16][17][18]…”
Published by United Scientific Group
AbstractProtein X-ray crystallography will remain the most powerful method to obtain the protein 3D atomic structures in foreseeable future. However, the production of the protein crystal as well as it quality (order, intensity of diffraction, radiation stability) remains the major problem. Many important proteins including those of life science interest and pharmaceutical industry impact are difficult to crystallize. The second major problem in protein crystallography is radiation damage of obtaining crystals which can only be partially overcome by existing methods. In the present work we use the protein LB nanotemplate crystallization methodgeneralized procedure for triggering of crystallization of any given protein, which allows to obtain radiation stable and high quality diffracting crystals for further X-ray analysis by synchrotron radiation. We apply LB nanotemplate method to crystallization of L-asparaginase from Rhodospirillum rubrum. This protein has potential application for combined chemical and enzymatic therapy of malignant blood disorders and therefore for new anticancer drug development. We also compare the diffraction quality of asparagines crystal obtained by classical method and LB nanotemplate and report preliminary X-ray diffraction characterization by synchrotron radiation.
L‐Asparaginases (ASNases) catalyze the hydrolysis of L‐Asn to L‐Asp and ammonia. Members of the ASNase family are used as drugs in the treatment of leukemia, as well as in the food industry. The protomers of bacterial ASNases typically contain 300–400 amino acids (typical class 1 ASNases). In contrast, the chain of ASNase from Rhodospirillum rubrum, reported here and referred to as RrA, consists of only 172 amino acid residues. RrA is homologous to the N‐terminal domain of typical bacterial class 1 ASNases and exhibits millimolar affinity for L‐Asn. In this study, we demonstrate that RrA belongs to a unique family of cytoplasmic, short‐chain ASNases (scASNases). These proteins occupy a distinct region in the sequence space, separate from the regions typically assigned to class 1 ASNases. The scASNases are present in approximately 7% of eubacterial species, spanning diverse bacterial lineages. They seem to be significantly enriched in species that encode for more than one class 1 ASNase. Here, we report biochemical, biophysical, and structural properties of RrA, a member of scASNases family. Crystal structures of the wild‐type RrA, both with and without bound L‐Asp, as well as structures of several RrA mutants, reveal topologically unique tetramers. Moreover, the active site of one protomer is complemented by two residues (Tyr21 and Asn26) from another protomer. Upon closer inspection, these findings clearly outline scASNases as a stand‐alone subfamily of ASNases that can catalyze the hydrolysis of L‐Asn to L‐Asp despite the lack of the C‐terminal domain that is present in all ASNases described structurally to date.
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