Mining of Novkitasetaline, a New Sulfur-Containing Antimalarial β-Carboline Alkaloid, from Streptomyces sp. PRh3 by Functional Ribosome Engineering Directed Heterologous Expression

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The supplementary material reports 1D and 2D spectra and the structural formulas of the corresponding molecules. However, no association is reported between the labelling of atoms in the structure and the signals in the spectra.

Furthermore, the Materials and Methods section does not provide any experimental details on the acquisition of NMR spectra or MS spectra.

There are errors in the header row of Table 1, main text: the unit of measurement for chemical shift is ppm. 

 

Comments on the Quality of English Language

The English needs a thorough revision.
This version contains so many grammatical errors that it is difficult to read.

Author Response

Please see the attachment about the point-by-point response to the reviewer’s comments 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors The article by Chen et al entitled "Mining of Novkitasetaline, a New Sulfur-Containing Antimalarial B-Carboline Alkaloid, from Streptomyces sp. PRh3 by Ribosome Engineering Directed Heterologous Expression" described a discovery of a Streptomyces strain isolated from Dongxiang wild rice, which mutation of its ribosome gene by exposure to rifampicin, generates a novel sulfur-containing alkaloid with antimalarial activity. The authors identified this new compound, elucidated its chemical structure and tested it in inihibition of Plasmodium. The article is in general correct, and the data is presented in a suitable fashion, yet it requires minor modifications in order to be suitable for readers. At 3.1 Is the rifampicin induced ribosomal mutation a standard practice for activation of production of new compounds? The authors mentioned it briefly in the introduction but the actual mechanism is not explained. Why is mutation in the ribosome leading to increased production of specific compounds? My main issue with the paper is that the authors do not really explain how the ribosome engineering combined with heterologous expression of ksl led to production of a novel compound. Do those genes produce novkitasetaline in other organisms? Or is novkitasetaline a result of some other reaction that happens in the host, and the novkitasetaline production is a consequence of improved ksl expression? Fig 4 shows this final reaction with indolmethylamine, but nothing about how this reaction happens is presented. Do other organisms that produce kitasetaline also conduct this reaction, or is it specific to the strain used in the manuscript? This needs to be addressed. Is there any potential mechanisms for how novkitasetaline acts? The presented data only show the effect on the organism as whole, but there is no discussion of its potential therapeutic mechanism, possible targets.   The data presented in Fig. 6 at first glance suggest the effect is very modest, could the authors compare the effects of novkitasetaline to other antimalarial drugs in the discussion? It would help the reader judge the discovery.   The manuscript requires proof-reading and correction of grammar, just a few examples: l. 20 abstract "to activate it produce" - "to activate production of" l. 303 duo - due l. 307 containing   References seem to be numbered wrongly, the first mentioned paper in the manuscript is 3 (l. 39). I don't see any mentions of ref 1 and 2. Comments on the Quality of English Language

The article needs proof-reading, many sentences are not correct or words are missing.

Author Response

Please see the attachment about the point-by-point response to the reviewer’s comments 

Author Response File: Author Response.pdf