Rabbit polymorphonuclear neutrophils form ³⁵S-labeled S-sulfo- calgranulin C when incubated with inorganic [³⁵A]sulfate

Rabbit peritoneal polymorphonuclear neutrophils reduced inorganic [³⁵S]sulfate to [³⁵S]sulfite in vitro, concomitant with incorporation of ³⁵S into a 10.68-kDa cytosolic protein as a S-[³⁵S]sulfo-derivative. Amino- terminal sequencing of the purified protein identified calgranulin C, a member of the S100 protein family. cDNA clones of calgranulins B and C were isolated using oligonucleotide primers based on the established amino acid sequences of other mammalian calgranulins. The complete amino acid sequence of rabbit calgranulin C was deduced from the nucleotide sequence of the corresponding cDNA. It comprises 91 amino acid residues, has a calculated molecular mass of 10.52 kDa, has 74% identity with porcine calgranulin C, and shows high homology with other S100 calcium-binding proteins. Rabbit calgranulin C has a single cysteine residue at position 30, which we believe to be modified to S- [³⁵S]sulfo-cysteine as a consequence of sulfate reduction by neutrophils. The formation of S-[³⁵S]sulfo-calgranulin C appears to be a reaction specific to neutrophils. The specific radioactivity of calgranulin C from the neutrophil culture medium was 50-fold greater than that of the calgranulin C within the cells, suggesting that S-sulfation of calgranulin C might be associated with its secretion.