Rat brain S-100 (S-100b) and ox brain S-100a0, S-100a and S-100b have been tested for their ability to control the assembly and disassembly of brain microtubule proteins in the presence of either Ca2+ or Zn2+, in vitro. In the presence of Ca2+, single S-100 isoforms have similar, if not identical, effects, i.e. they inhibit assembly and promote disassembly. In the presence of Zn2+ from 0.1 to 1 mM (free concentration), rat S-100 and ox S-100a and S-100b inhibit assembly, while S-100a0 is without effect. These data are briefly discussed in relation to the cellular localization of single S-100 isoforms in the brain.

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Quantitative determination of S-100 protein content on human melanoma tissues and in sera of melanoma patients was made possible through radioimmunoassay (RIA). Melanoma tissue extracts prepared from metastatic sites in both skin and lymph nodes contained 0.08-2.80% of S-100 out of the total extractable proteins, and it was also noticed that the tumors obtained from lymph-node metastasis possessed slightly higher levels of S-100 as compared with those obtained from the skin lesions. Serum S-100 levels of 12 melanoma patients with Stage 1 to 3 diseases were also examined by means of RIA, but only two patients showed a slight elevation of serum S-100 levels. When tissue sections prepared from a variety of cutaneous tumors, including pigmented nevus, melanoma and Schwannoma, were stained for S-100 by an immunoperoxidase technique, these tumors of neuroectodermal origin were demonstrated to contain a detectable amount of S-100, whereas other tested nonmelanocytic and non-neurogenic tumors were entirely negative for S-100. These data stress the usefulness of S-100 for the diagnosis of neurogenic and melanocytic tumors, especially melanomas, despite the difficulty of its detection in the sera of the tumor bearers, which might reflect the low tendency of S-100 to be shed from the tumor cells.

Retention times were estimated for eleven-tryptic peptides of calmodulin, calmodulin and S100 protein on the various reversed phase under the same elution condition, that is, linear gradient system from 20 % (v/v) to 75 % acetonitrile in 0.1 % (v/v) trifluoroacetic acid. The comparison of retention times was performed on the various combinations of the columns: Polystyrene (Hitachi-E302 BUNSEKI KAGAKU Vol. 33(1984) tion of the accumulated values on alkyl bonded silica in the literatures to those on polystyrene resin and vice versa. EXPERIMENTAL Proteins and peptides Calmodulin and S100 protein were purified from bovine brain soluble extracts by ammonium sulfate fraction and following column chromatography proce-dures32)-34). L-(1-tosylamido-2-phenyl) ethyl chloromethyl ketone (TPCK)-treat-to thank Dr.K.Seta of Taisho pharmaceutical Co., Ltd. for valuable suggestions. They are also indebted, for the donation of packing materials, to Drs. Y. Kato and K.Nakamura of Toyo soda Manufacturing Co ., Ltd.

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