Protein Termini

Since the first and the last residues of a protein have peculiar properties, unique amongst all residues, they have been analyzed repeatedly during the last decades. In this brief review, I try to summarize, besides the biochemical roles, the five features that have attracted most attention: (i) the Euclidean distance between the N- and C-termini and its relevance to protein folding, (ii) the reason why the termini are solvent exposed, (iii) the backbone conformation of the termini, (iv) the amino acid composition of the termini, and (v) the role of the termini in protein crystallization. Each of these five issues, which deserve attention nowadays thanks to the availability of massive amounts of data, is accompanied by my personal outlook of the research in the field.