genes make alpha beta gamma subunits (proteins) to be used in making sodium channels... If I understand correctly? And so, since the genes keep making those subunits, does that mean new sodium channels are continuously being made with those proteins till you die? In other words, if those genes suddenly stop making the subunits in your 50's or something, your sodium channels will disappear or stop working? (Probably unrealistic, but theoretically...)

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    $\begingroup$ This is your second question about sodium channels that seems to show some misunderstandings about genetics, gene expression, and protein expression. So far, you've just used the term "sodium channel", I suggest you read the wiki page, then ask about a specific sodium channel, or at least offer more details. I am also having trouble understanding what you're asking. Are you asking if 1 gene makes multiple copies of the protein it codes for (it does) or are you asking if 3 individual protein subunits make multiple proteins (they don't). $\endgroup$ – user137 Apr 20 '15 at 21:19
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    $\begingroup$ Please do some research on protein turnover. Sodium channels, or any other protein or protein complex, are not just created early in life, then stay where they are until the organism dies. Cells are constantly dying and being replaced, and within a single cell proteins are constantly being degraded and new ones made. For some proteins the half-life is seconds or minutes, for others it can be hours, days, or longer, but eventually it all gets renewed. I suggest you do some more background reading on cell biology - Molecular Biology of the Cell is a good start. $\endgroup$ – MattDMo Apr 20 '15 at 21:33

You are asking about two different processes: turnover (degradation) of mRNA and turnover of proteins. In a typical mammalian cell the mRNA half-lives of stable messages approach the length of the cell cycle (e.g. 24 hr). One mRNA could be translated around the clock if needed. The resulting proteins will also have a measurable half-life, and that will vary with the protein and the cellular conditions. If a cell ran out of protein and its mRNA there is often a feedback loop that activates transcription of the structural gene back in the nucleus.

  • $\begingroup$ Feedbacks are not essentially always present. $\endgroup$ – WYSIWYG May 22 '15 at 7:12

You should really study the basics before asking specifics about a particular protein. I am not voting to close the question, however.

DNA catalyses the formation mRNA (transcription) which in turn catalyses the formation of a polypeptide (translation); RNA polymerase and ribosome are co-catalysts respectively.

A functional protein may have many polypeptide chains as in the case of Sodium channel (or even haemoglobin). The function of the protein complex may be compromised if:

  • The polypeptides chains are not formed
  • The polypeptide chains are not associating properly

The former can result either because of a block in translation or a block in the transcription. These blocks can also arise because of active regulation in response to a certain condition; this is a temporary change.

Mutations can lead to loss of function by either causing transcription/translation blocks or abolishing interaction between different polypeptides.

In a cell all biomolecules are continuously formed and degraded. The rate at which they are degraded is called the turnover. If a steady level has to be maintained then turnover rate should be balanced by the formation rate.

When formation is abolished then different biomolecules will disappear at a speed proportional to their degradation rates.
If the mutation causes a loss of association of polypeptides then non-functional proteins will replace the functional ones with rate proportional to the degradation rate. (NOTE: Formation rate of a protein is proportional to the available mRNA).

Most intracellular and membrane proteins have high turnover. Extracellular structural proteins such as collagen have a relatively low turnover. So if sodium channel gene stops transcribing the effects would be felt very soon.


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