Sulfur Amino Acids: From Prebiotic Chemistry to Biology and Vice Versa.

Two sulfur-containing amino acids are included in the list of the 20 classical protein amino acids. A methionine residue is introduced at the start of the synthesis of all current proteins. Cysteine, thanks to its thiol function, plays an essential role in a very large number of catalytic sites. Here we present what is known about the prebiotic synthesis of these two amino acids and homocysteine, and we discuss their introduction into primitive peptides and more elaborate proteins. 1 Introduction 2 Sulfur Sources 3 Prebiotic Synthesis of Cysteine 4 Prebiotic Synthesis of Methionine 5 Homocysteine and Its Thiolactone 6 Methionine and Cystine in Proteins 7 Prebiotic Scenarios Using Sulfur Amino Acids 8 Introduction of Cys and Met in the Genetic Code 9 Conclusion [ABSTRACT FROM AUTHOR]