Vv. Ivanenkov et al., CHARACTERIZATION OF S-100B BINDING EPITOPES - IDENTIFICATION OF A NOVEL TARGET, THE ACTIN CAPPING PROTEIN, CAPZ, The Journal of biological chemistry, 270(24), 1995, pp. 14651-14658
Short amino acid sequences that interact with the Ca2+ binding protein
S-100b were identified by screening a bacteriophage random peptide di
splay library. S-100b binding bacteriophages were selected by Ca2+-dep
endent affinity chromatography, and the sequence of the random peptide
insert contained in 51 clones was determined. Alignment of the sequen
ce of 44 unique S-100b binding peptides identified a common motif of e
ight amino acids. A subgroup of peptides that contained sequences with
the highest degree of similarity had the consensus motif (K/R)(L/I)XW
XXIL, in which predominantly P, S, and N were found in position 3, and
S and D were found in position 5. Analysis of sequence databanks iden
tified a similar sequence in the COOH-terminal region of the alpha-sub
unit of actin capping proteins. The peptide TRTKIDWNKILS (TRTK-12), co
rresponding to the region of greatest homology within this region of t
he subunit of actin capping proteins (e.g. amino acids 265-276 in CapZ
alpha 1 and CapZ alpha 2), was synthesized and shown by fluorescence
spectrophotometry to bind S-100b in a Ca2+-dependent manner. Gel overl
ay and cross-linking experiments demonstrated the interaction of S-100
b with CapZ to be Ca2+ dependent. Moreover, this interaction was block
ed by addition of TRTK-12 peptide. These results identify Ca2+-depende
nt S-100b target sequence epitopes and designate the carboxyl terminus
of the alpha-subunit of actin capping proteins, like CapZ, to be a ta
rget of S-100b activity. The high level of conservation within this re
gion of actin capping proteins and the apparent high affinity of this
interaction strongly suggest that the interaction between S-100b and t
he alpha-subunit of actin capping proteins is biologically significant
.