Identification of P8,14 As a Highly Abundant Heterodimeric Calcium Binding Protein Complex of Myeloid Cells

In this report we describe the biochemical characterization of neutrophil and monocyte p8 and p14. Together the two proteins comprise approximately 45% of cytosolic protein in neutrophils and approximately 40-fold less in monocytes. They fractionated together in several chromatographic procedures and were found to exist as a noncovalently associated complex with a stoichiometry of 1:1, named p8,14. Cross-linking experiments showed p8,14 to form heterodimers under conditions simulating the cytosol. An apparent molecular mass of 35,000 daltons was obtained for the p8,14 complex in molecular sizing experiments which suggests the presence of modifications or distinctive structural features. Two major forms of p14 can be identified by two-dimensional gel electrophoresis, both of which form heterodimers with p8. The lower molecular weight variant of p14 lacks Cys-3 (Met-Thr-Cys-Lys-Met...) suggesting that differing translational start sites account for these two forms of p14. A protocol has been devised for the rapid purification of milligram quantities of p8 and p14 from neutrophil cytosol using fast-protein liquid chromatography.