Photograph of Methionine under the microscope.

Methionine is an important amino acid that helps to initiate translation of messenger RNA by being the first amino acid incorporated into the N-terminal position of all proteins. This sulfur-containing amino acid is also the source of sulfur for cysteine in animals and man. In that regard, methionine is considered an essential amino acid whereas cysteine is not, so cysteine is nonessential only as long as the diet contains adaquate amounts of methionine. The terminal methyl group of the methionine side chain often participates in biochemical methyl transfer reactions making methionine a member of the "methyl donor" class of biochemicals. On a molar basis, methionine is incorporated into proteins and enzymes at the rate of 1.7 percent, but this is partially due to posttranslational protein-modifying events that often occur where methionine and several other N-terminal amino acids are removed from the protein.

© 1995-2022 by Michael W. Davidson and The Florida State University. All Rights Reserved. No images, graphics, software, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.
This website is maintained by our
Graphics & Web Programming Team
in collaboration with Optical Microscopy at the
National High Magnetic Field Laboratory.
Last modification: Monday, Jul 02, 2018 at 04:20 PM
Access Count Since April 11, 1998: 73548