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Brunner Syndrome: could truncated MAO protein cause problem?

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Brunner Syndrome: could truncated MAO protein cause problem?

Postby thetada1 » Fri Dec 11, 2015 12:13 pm

Hi everyone,

This is my first post on this forum. I'm a chemistry teacher and science writer who is limitlessly fascinated by biochemistry / molecular biology. This question has arisen from a piece of science writing I'm doing. Thanks in advance for any help anyone can provide.

Brunner syndrome has been linked to the protein monoamine oxidase A. A mutation in the gene causes the protein to be truncated, severely curtailing the ability of affected persons to metabolise monoamines. The syndrome causes problems including insomnia, mental retardation and aggressive or violent outbursts.

Since I am writing about the condition, there is a line of inquiry I want to consider, which is this: is it possible that the truncated protein causes and or contributes to the phenotype? It seems to be assumed that the excess of monoamine transmitters, dopamine, serotonin and the like, is what causes the problems. What I'm wondering is whether the truncated protein itself could cause problems. In other words, is it the absence of monoamine oxidase that causes the problems, or the presence of truncated monoamine oxidase?

From what I can tell, it is the excess of neurotransmitters that is more likely to cause the problems. My main reason for thinking so (other than that's what the relevant researchers are saying) is that there appear to have been up to three different varieties of mutation in the MAO A gene, all of which cause the same basic phenotype. It's just for a sense of completeness in writing about the topic that I want to say, as scientists, we need to consider all possibilities and one possibility is that the truncated protein causes the problem. Then, more science, evidence suggests no, but it's good that we looked down that route just to be sure. My concern is that there might be something ignorant about saying this. For example, does the body have a clean up system to get rid of truncated proteins? (Again, doesn't seem likely, but it's an example of something I might not have thought about, which would therefore make me look like an idiot if I suggest the potential role of the truncated protein.)

Some relevant reading:

A good overview of Brunner syndrome and other material on the potential link between MAOA and violence can be read in chapter 12 of the below linked book. (Skip to p.179, most / all of the chapter is available free in the google books preview.)

https://books.google.co.uk/books?id=Bmy ... ne&f=false

Novel monoamine oxidase A knock out mice with human-like spontaneous mutation

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3435113/

New insights into Brunner syndrome and potential for targeted therapy

http://onlinelibrary.wiley.com/doi/10.1 ... 9/abstract

Again, thanks if anyone can help. I'd really appreciate it.
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Re: Brunner Syndrome: could truncated MAO protein cause prob

Postby claudepa » Sat Dec 19, 2015 5:21 pm

Hi. You have already a very good knowledge of biochemistry. I do not know the Brunner Syndrome. However I can tell that mutated proteins are not necessarily eliminated by the cell. They can create diseases such as cancers because of their abnormal structure. For instance in cancer the ras protein (always activated after mutation whereas non mutated ras is activated only after binding GTP) or the fusion proteins created by fusion of two genes moieties that can work as abnormal transcription factors, wrongly regulating target genes. Of course if the catalytic part of the monoamine oxydase would be in the C terminal part, the trucated protein would act as if no monoamine oxydase is present.
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