S100B protein in clinical diagnostics: assay specificity.

Abstract

S100 proteins/antibodies have received increasing attention because of their use in the diagnosis of several human diseases and as predictive markers of improving clinical management, outcome, and survival of patients (1)(2). S100 proteins also have a great potential as drug targets to improve therapies. Unique to the S100 family is the location of 16 S100 genes in a gene cluster on human chromosome 1q21; this led to the introduction of the widely accepted nomenclature shown in Table 1⇓ . Four additional S100 genes, including S100B , are located on different chromosomes [for reviews, see Refs. (1)(3); for S100A15 , see Ref. (4); for S100A16 , see I. Marenholz and C.W. Heizmann, Characterization of S100A16, an ubiquitously expressed EF-hand protein which is upregulated in tumors, submitted for publication]. S100 proteins are 10–12 kDa in size and form homo- and heterodimers. The monomer is composed of two helix-loop-helix (EF-hand) motifs connected by a central hinge region (1)(3). The C-terminal EF-hand contains the canonical Ca2+-binding loop, common to all EF-hand proteins (e.g., troponin C or calmodulin). The N-terminal EF-hand consists of 14 amino acids and is characteristic of S100 proteins. S100 proteins show different degrees of homology, ranging from 25% to 65% identity at the amino acid …