Inhibition of protein synthesis in ..

In yeast, we found that S215F and P95L/E145K induced depurination and inhibited protein synthesis similarly to WT preRTA but did not induce nuclear fragmentation and ROS generation, hallmarks of apoptosis. In addition, G212E had low biological activity and did not affect any of these endpoints (). Expression of pre- and mature forms of each of these three mutants reduced depurination levels to 60% of WT RTA control levels in mammalian cells at 19 h after transfection. This lower level of depurination was still sufficient to inhibit protein synthesis by 80 to 90% relative to the vector control. Interestingly, the pre-forms of G212E, S215F, and P95L/E145K did tend to have higher levels of protein synthesis compared to the mature forms or WT preRTA when expressed in mammalian cells, although protein synthesis was still only 15 to 20% of vector control levels. However, they produced full caspase activation, nucleosome accumulation and JNK/p38 signaling. These results indicate that depurination can be reduced by as much as 40% in mammalian cells with minimal effects on protein synthesis inhibition and activation of stress-activated signaling cascades and apoptosis. A substantial reduction in depurination as was observed with pre E177Q may be necessary to prevent protein synthesis inhibition by RTA, possibly due to the high sensitivity of mammalian ribosomes to RTA.

RIP30A - Protein synthesis inhibitor II - Hordeum …

A protein synthesis inhibitor is a substance that stops or slows the growth or proliferation of ..

Inhibits the elongation phase of protein synthesis

To investigate if apoptosis was induced in the transfected cells, activation of caspase 3/7 was investigated in MAC-T cells 19 h after transfection (). Caspase activity was induced similarly by pre- and mature WT RTA (2.7 ± 0.2 and 2.8 ± 0.2-fold, respectively; mean ± SE of 9 experiments) relative to vector controls. The active site mutant E177K elicited negligible caspase activation which corresponded with the lack of ribosome depurination and protein synthesis inhibition. In contrast the pre- and mature forms of E145K, G212E and P95L/E145K as well as mature S215F activated caspase activity to the same degree as their respective WT RTA controls. PreS215F activated caspase 3/7 to a lesser extent than WT preRTA, which corresponded with decreases in depurination and protein synthesis inhibition. The E177Q mutant also showed a difference between the pre- and mature forms in terms of caspase activation, with mature E177Q eliciting a greater increase in caspase 3/7 activity relative to preE177Q. Interestingly, both the pre- and mature forms of P95L activated caspase to a greater extent relative to their WT counterparts.

Protein synthesis inhibitor : Wikis (The Full Wiki)

A GFP transfection assay was used to determine if protein synthesis inhibition corresponded with changes in ribosome depurination. Overall, the pattern of ribosome depurination observed with the mutated RTA proteins was reflected in the degree of protein synthesis inhibition (). Fluorescence was almost nondetectable in cells transfected with pre- or mature WT RTA relative to cells transfected with plasmid vector alone. Similar results were obtained with P95L, which depurinated ribosomes similarly to WT RTA based on qRT-PCR results. Pre- and mature E177K did not inhibit protein synthesis which corresponded with the very slight degree of depurination observed. Protein synthesis levels observed with pre- and mature E177Q were intermediate between E177K and the other mutants. Surprisingly, a greater level of inhibition of protein synthesis was observed with mature E177Q (60% inhibition of vector controls) compared to preE177Q (40% inhibition of vector controls) even though they showed similar levels of depurination at 19 h after transfection. Protein synthesis was inhibited significantly less relative to WT RTA for preP95L/E145K and for pre- and mature S215F and G212E, however, this still represented an 80 to 90% inhibition of protein synthesis relative to vector controls. Interestingly, the mature RTA mutants tended to have a greater effect on protein synthesis inhibition than their preRTA counterparts. Specifically, preE177Q, P95L/E145K, S215F and G212E inhibited protein synthesis less than their corresponding mature forms and less than WT preRTA.

15/04/1976 · Inhibition of protein synthesis in vitro by crotins and ricin
A protein synthesis inhibitor is a substance which stops or slows the growth or proliferation ..

Protein Synthesis Inhibitors ~ Biology Exams 4 U

The RAW264.7 cells treated with RTB (10 μg/ml) inthe presence of genistein, SB203580, LY294002, or staurosporine for24 h exhibited reduced NO production (). Similar results were obtainedfor the mRNA expression of iNOS by RT-PCR (). Of note, themitogen-activated protein kinase (MAPK) inhibitors, PD98059 andSP600125, did not affect the observed RTB-induced NO production().

Inhibitors of Transcription & Translation Flashcards | …

Compound 8 (7CP) was soaked into RTA crystals and X-ray data collected to 1.29 Å resolution. shows the electron density for the bound 7CP and shows details of the interaction with the protein. As seen in previous structures of RTA in complex with pterin derivatives, the 2-amino group of the pterin ring donates one hydrogen bond each to the carbonyl oxygen atoms of Val81 and Gly121, and the 4-oxo and N5 atoms accept hydrogen bonds from Arg180 []. The tautomeric form of the pterin with a proton on N1 is favored so that N1 can donate a hydrogen bond to a carboxyl oxygen of Gly121 and N3 can accept a hydrogen bond from the amido-N of Val81. An additional hydrogen bond, which was not seen in the previous 6-substituted pterins, is made between the amido-N of Tyr123 and the carbonyl oxygen of the 7-carboxy group. This extra hydrogen bond is retained in all subsequent derivatives based on this platform, likely contributing to the general increase in potency of this series of pterin-based inhibitors over previous ones.

(protein synthesis inhibitor) Rifamycin

An early effort centered on attaching a soluble carboxylate to the pterin platform. It was previously observed that 6-carboxypterin had little or no detectable inhibition and showed no electron density when soaked into RTA crystals []. However, the newly synthesized, regioisomeric 7-carboxy pterin, 7CP, is one of the more potent small molecule inhibitors of RTA we have observed. This led to a paradigm shift in the direction of our pterin-based synthesis, as most pterin chemistry focuses on the 6-substituent due to similarities to naturally occurring folic acid []. We discuss herein the results of 7CP in an in vitro translation assay, a differential scanning fluorimetry (DSF) assay, as well as the X-ray structure of this new inhibitor bound into the active site of RTA. We also discuss the construction of new 7-substituted pterins and their subsequent results in these various assays, with many new compounds resulting in μM inhibition. We report two key X-ray structures in this paper; the full crystallographic description of all these structures will soon be released independently.