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Name: Rhonda D.
Status: Educator
Age: 20s
Location: N/A
Country: N/A
Date: 2002

What is the maximum number (to date) of amino acids in a protein chain? One of my inquiring students wants to know. We know that one is the minimum, but what is the record maximum?

Rhonda, There are many proteins in the thousands range. I used to work on a protein called "fat" that was over 5000 amino acids. A great many proteins are listed at the GenBank site, although it will take a bit of work to extract the information you want. For starters, look up the muscle protein called "titan" (I think that is the name). As I recall, that was one of the largest I had seen. By the way, one amino acid is not generally considered a protein.

Paul Mahoney, PhD

First off, one amino acid, does not make a chain...two is the minimum. I give you examples of protein sizes in kilodaltons. Milk lipase...6.7; Myoglobin...16.9; catalase 222; The largest I know of is...Turnip yellow mosaic virus protein at a whopping 3013 kD ! (a Dalton is 1/12 the mass of a carbon atom)...a kilodalton = 1000 daltons. To put this in perspective.... Cytochrome C protein has 103 amino acids and weighs in at 13.4 kilodaltons. Insulin is rather small and has 51 amino acids. Hemoglobin is rather large, One hemoglobin molecule is made up of 4 polypeptide (biologists prefer to use polypeptide for the parts of a multichain protein) chains: two alpha chains, each with 141 amino acids and two beta chains, each with 146 amino acids...which gives 574 amino acids in this one multichained (oligometric) protein.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy

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