Zinc finger motif

Another group of proteins are called zinc fingers
because they resemble fingers (see D). They are
involved in important functions during embryonic
development and differentiation. The basic
zinc finger motif consists of a zinc atom connected
to four amino acids of a polypeptide
chain. Here, two histidine (H) and two cysteine
(C) residues are shown in the schema on the
left. The three-dimensional structure on the
right consists of an antiparallel " sheet (amino
acids 1–10), an ! helix (amino acids 12–24),
and the zinc connection. Four amino acids, cysteines
3 and 6 and histidines 19 and 23, are
bonded to the zinc atom and hold the carboxy
(COOH) end of the ! helix to one end of the "
sheet.