S-100 are small dimeric acidic calcium and zinc-binding proteins [1] abundant in the brain. They have two different types of calcium-binding sites: a low affinity one with a special structure and a 'normal' EF-hand type high affinity site. The vitamin-D dependent intestinal calcium-binding proteins (ICaBP or calbindin 9 Kd) also belong to this family of proteins, but it does not form dimers. In the past years the sequences of many new members of this family have been determined (for reviews see [2,3,4]); in most cases the function of these proteins is not yet known, although it is becoming clear that they are involved in cell growth and differentiation, cell cycle regulation and metabolic control. These proteins are:

• Calcyclin (Prolactin receptor associated protein (PRA); clatropin; 2a9; 5B10; S100A6).
• Calpactin I light chain (p10; p11; 42c; S100A10).
• Calgranulin A (cystic fibrosis antigen (CFAg); MIF related protein 8 (MRP- 8); p8; S100A8).
• Calgranulin B (MIF related protein 14 (MRP-14); p14; S100A9).
• Calgranulin C.
• Calgizzarin (S100C).
• Placental calcium-binding protein (CAPL) (18a2; peL98; 42a; p9K; MTS1; metastatin; S100A4).
• Protein S-100D (S100A5).
• Protein S-100E (S100A3).
• Protein S-100L (CAN19; S100A2).
• Placental protein S-100P (S100E).
• Psoriasin (S100A7).
• Chemotactic cytokine CP-10 [5].
• Protein MRP-126 [6].
• Trichohyalin [7]. This is a large intermediate filament-associated protein that associates with keratin intermediate filaments (KIF); it contains a S- 100 type domain in its N-terminal extremity.

A number of these proteins are known to bind calcium while others are not (p10 for example). Our EF-hand detecting pattern (see <PDOC00018>) will fail to pick those proteins which have lost their calcium-binding properties. We developed a pattern which unambiguously picks up proteins belonging to this family. This pattern spans the region of the EF-hand high affinity site but makes no assumptions on the calcium-binding properties of this site.