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Posts Tagged ‘heparan sulfate’


Some months before @robField’s tweet setting off the train that led to the Eu sensor that discriminates PAP/PAPS, Ed Yates and myself were having a curry with Dulce Papy-Garcia from UPEC, who had examined one of our PhD students. A matter we discussed at length was ‘why sulfate’. That is, why does biology use both sulfate and phosphate to modify post synthesis proteins, polysaccharides and other molecules. We didn’t come up with an answer,  but the conversation led Ed and myself to consider that the question merited exploration. 

This we thought would be a simple matter. 

It turned out to be one of the most difficult papers Ed and myself have written, to the extent that after N drafts (where N is a significantly larger number than either of us had experienced in any previous writing exercise) and too many summers we still had nothing satisfactory. So, we cunningly inveigled two colleagues, Tim Rudd from NIBSC and Marcelo Lima from Keele to join us on what we advertised as the sunny beach of sulfate and phosphate, but which in reality was a rather dank quagmire. There is though something about strength in numbers, and with very helpful input from Steve Butler in Loughborough, we arrived at what we considered a satisfactory synthesis. Happily, the reviewers concurred, and the paper is now published at Royal Society Interfaces, “Phosphorylation and sulfation share a common biosynthetic pathway, but extend biochemical and evolutionary diversity of biological macromolecules in distinct ways”.

This is by no means the last word on the matter, but along with some previous thoughtful papers we cite (if we have missed one, please let me know) it provides some ideas that may help us to understand why biology co-opted particular elements from the inorganic world to perform groups of functions vital to life as we know it now.

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More sulfation

Earlier this year Simon Wheeler (who now has a well deserved substantive position, congratulations!) and Steve Butler published the first output from the BBSRC TDRI awarded to Steve, with myself and Ed Yates in supporting roles. It is always nice to collaborate with real chemists, as it reminds me I am very much a pseudo chemist, and I learn a lot. After what I would consider a quite heroic effort on the synthesis front, Simon and Steve pulled out a very useful sensor, based on a europium complex. The Eu sensor has good selectivity for PAP over PAPS, the universal sulfate donor. The assay works well and is very amenable to high throughput 384 well format assays (= more papers on the way). So we can now measure sulfotransferase activity in realt-ime independently of the acceptor for pretty much any enzyme-substrate combination. This represents an important tool for the wider sulfotransferase community. 

The paper also demonstrates the importance of social media in science, as a means to access in a non-direct manner new information that sets off an innovative project. I saw tweet from @Fieldlab highlighting a paper from Steve’s lab on lanthanide sensors able to discriminate nucleotide phosphates and read the paper. Naively I thought PAP/PAPS sensing using such compounds should be easy, so I contacted Steve. After some preliminary tests with PAP and PAPS on his side, we wrote the grant – another lesson here, as the application neared final from I went over to Loughborough for a meeting, which allowed us to iron out a few problems far more effectively than by electronic communication. The work was, as hinted above, far from straightforward, but like everything that is new, very rewarding and continues to be so.

I have just moved from the bird site to the proboscidean one and things look like there will be even more of such ‘random access’ of information there, so let’s see what turns up!

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After an interaction on Twitter with a colleague who is associated with #LongCovid and #TeamClots, he asked me for some references. I thought what to send, and then realised that references plus something a bit more than a Tweet might be useful, so here goes.

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With new data in hand, our first preprint on SARS-cov-2 receptor binding domain (RBD) interacting with heparin now has a sibling, which demonstrates that heparin inhibits the infection of Vero cells by SARS-cov-2

Some of the key points of the team’s new work are:

  1. Inhibition of viral infectivity in a Vero cell model by heparin, which is a better inhibitor for SARS-cov-2 than SARS-cov.
  2. Analysis of the interactions of a more extended library of model heparins with the SARS-cov-2 receptor binding domain. As with many other heparin-binding proteins, these data show that while sulfation is critical for RBD binding, the amount of sulfate is not, but instead it is the spatial arrangement of sulfate groups that is most important.

Together the data point to heparin being a potentially useful therapeutic to reduce infectivity. (more…)

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Today was the culmination of Zaid’s PhD journey, when he successfully defended his thesis on the use of gold nanoparticles to probe the mechanism of action of a peptide that inhibits ‘flu virus infectivity. Though he approached his viva with trepidation, his beaming face afterwards told a different story. The usual smattering of corrections, a paper already up on Bioarxiv ready to submit for peer review and another to put up on Bioarxiv, and in a few weeks he will be truly done, with a CV to match.

 

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Congratulations to Aiseta!

On Monday 4 December Aiseta Baradji successfully defended her thesis. A long journey and a hard one as ever with its ups and downs, surprises and a certain amount of head scratching over data that push us in new directions. In the end a great thesis that will be consulted in the labs of her supervisors for a long time. Now onto the next phase.

 

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Two postdoc positions are available in my lab.

Both are part of the larger, European Commission-funded FET-Open programme, ArrestAD, which has recently been funded.

Position 1 aims to characterise heparin-binding proteins in Alzhiemer’s disease.

Position 2 aims to develop inhibitors to Golgi sulfotransferases. (more…)

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Our review on fibroblast growth factors (FGFs) as tissue repair and regeneration factors, which we made available as a preprint from the time of submission is now published at PeerJ. (more…)

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Of nanoparticles, cells and polyanions

It is the end of semester 2 so it’s marking season. Since we double mark (a good thing), the final year research projects are marked by both supervisor and an assessor, a member of staff who is not involved in the project. One of the projects I marked was Gemma Carolan’s on “How do SmartFlares RNA detection probes reach the cytosol? Available are the PDF of report, and posts here and here.

I had a sense of déjà vu while reading the project – the clear endosomal location of the SmartFlares, regardless of the DNA sequences brought me back to the days when antisense was the technology of the future for medicine.

While evaluating new technology it is useful to go back and look at other high flying technology. The reality is that it takes decades before we know whether the promise (and hype) were justified; this is true for any hot topic from stem cells to nanoparticles and graphene.

Antisense effects can be mediated by RNAse H, an enzyme that specifically cleaves RNA-DNA duplexes and which protects our cells from RNA viruses. There are other mechanisms, e.g., interference with splicing or translation, but the RNAse-H mediated transcript degradation should be central to many antisense effects. There were many papers reporting specific effects (evidenced by differences between sense, antisense and scrambled oligonucleotides sequences). These certainly contributed to success of individuals and of institutions, e.g., in UK Research Assessment Exercise and grant awards.
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I am a fan of PubPeer, as it provides a forum for discussion between authors and the wider community, something I have discussed in a number of posts (two examples being here and here). Two days ago, My colleague Mike Cross came by my office, having just delivered a pile of exam scripts for second marking (it’s exam and marking season), asking if I had seen a comment on our paper on PubPeer. I had not – too many e-mails and too busy to look at incoming!
So I looked at the question, which relates to panels in two figures being identical in our paper on neuropilin-1 and vascular endothelial growth factor A (VEGFA) – indeed they are labelled as being identical.
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