Figure 1.

Organization of the human granzyme B gene. The gene is approximately 3.2 kb in length and is presented as a prototype of granzyme gene organization. A TATA box consensus sequence (T) is present approximately 30 bp from the initiation site for transcription. The five exons are indicated by Roman numerals. Exon I codes for the leader sequence. Exon II contains the start of the mature protein (highly conserved as IIGG (in the single-letter amino-acid code) in most granzymes) and encodes the first of the essential catalytic triad of residues at the active site, histidine (H). Exon III encodes the aspartic acid (D), and exon V the other essential catalytic residue, serine (S). The side chain of an Arg226 (R) forms the base of the substrate pocket and forms a salt bridge with aspartic acid at the P1 position of the substrate. The polyadenylation signal is shown as P. The lengths of the exons and introns of the human granzyme B gene are also shown in base-pairs, although these show minor variations between different granzyme genes. The 5' untranslated sequence is shaded.