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Simple and Easy biochemical question - (Dec/24/2008 )

This is not a homework question: I was reading in Deborah Goldberg's AP Biology and when I was reading about the 1952 Hershey and Chase experiment, I got really confused.

In the same book: "Proteins consist of the elements S[ulfur], P[hosphorus], C[arbon], O[xygen], H[ydrogen], and N[itrogen]." But what are proteins made of? Amino Acids connected by peptide bonds (and of course, in the secondary and tertiary structures, various bonds - i.e. hydrogen bonds, ionic bonds, etc.). If you will carefully look at a chart of amino acids, you will notice that NONE contain the atom of Phosphorus. So is the book wrong when they say that proteins are made of phosphorus? Additional evidence is this passage excerpted from the same book: "They tagged bacteriophages with the radioactive isotopes 32P and 35S. Since proteins contain sulfur but not phosphorous and DNA contains phosphorous but not sulfur, the radioactive 32P labeled the DNA of the phage viruses while 35 S labeled the protein coat of the phage viruses."

-thewax-

well I am not sure if this is what they meant, or how sensitive their equipment is.

But proteins do contain a very tiny little bit of phosphate, in the form of protein phosphorylation. If that is included, proteins also contain selenium, iron , zinc etc. Phosphorus isn't a primary building block of proteins, but proteins in general do contain a bit of phosphorus.

DNA on the other hand contains a lot of phosphate and it is a primary component.

Compared to the amount of phosphate present DNA, the signal from phosphorylated protein would be undetectable.

-perneseblue-

Thanks a lot, perneseblue!!!!!!!! smile.gif

I have a question: what does protein phosphorylation mean (I looked at wikipedia but I didn't really get what they were talking about)????????

Even with this protein phosphorylation, how would selenium, iron, zinc, etc. be considered part of phosphorous??????????????

-thewax-

Many proteins undergo posttranslational modification. They have connected to them -- covalently or ionically -- atoms or moleculrs that are not amino acids. The amino acids still form the backbone of the molecule, but it is frequently "decorated" with phosphorous, lipids, glycans, etc., or requires being bound to iron, zinc, etc. For example, hemiglobin (the oxygen-transporting protein in your red blood cells) requires iron-containing heme groups to work.

-HomeBrew-

Thanks!!!!!!! smile.gif

I see - so in the post-translational control, there are still some "non-amino acid" molecules stuck on them (and sometimes the proteins need them). So you're basically saying that yes, the amino acids do form the backbone of the protein, but more than often, the amino-acid chain needs a little more than just the amino acids to be really a protein (like selenium, iron, zinc, etc.), right???????????? And protein phosphorylation would just be describing how some of the "non amino acid" molecules are stuck on, right??????????????

Thanks again!!!!!!!!

-thewax-

QUOTE (thewax @ Dec 25 2008, 05:08 AM)
Thanks!!!!!!! smile.gif

I see - so in the post-translational control, there are still some "non-amino acid" molecules stuck on them (and sometimes the proteins need them). So you're basically saying that yes, the amino acids do form the backbone of the protein, but more than often, the amino-acid chain needs a little more than just the amino acids to be really a protein (like selenium, iron, zinc, etc.), right???????????? And protein phosphorylation would just be describing how some of the "non amino acid" molecules are stuck on, right??????????????

Thanks again!!!!!!!!


You might want to read this:
http://en.wikipedia.org/wiki/Post-translational_modification

-kristiansj-

cool... thanks!

-thewax-