Biomedical subjects

P Freemont

Publications and source records attributed to P Freemont.

4 recordsLinked to original sources

PubMed1991

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.

Blotting, Western↗

PubMed1991

Isolation and characterisation of a testis-expressed developmentally regulated gene from the distal inversion of the mouse t-complex.

We differentially screened a pool of mouse testis clones in order to identify genes important in germ cell development. One of the isolated clones was found to be expressed only in the male germ line where it is first detected at around the pachytene spermatocyte stage. This gene maps to a subregion of the t-complex in the distal inversion near, but not within, the tw18 and the th20 deletions. A comparison of the t and wild forms of the gene reveals a high degree of sequence conservation. This gene is associated with a CpG-rich island at its 5' end. It encodes a novel protein with extensive alpha-helical structure indicative of coiled-coil interactions.

Amino Acid Sequence↗

PubMed1989

Ionomycin-regulated phosphorylation of the myeloid calcium-binding protein p14.

Two associated calcium-binding proteins (CaBPs) have recently been identified specifically in cells of myeloid origin. These proteins have relative molecular masses (Mr) of 8,000 and 14,000 and are variously referred to as the cystic fibrosis antigen, the L1 light chain, MRP-8 or p8, and the L1 heavy chain, MRP14 or p14, respectively. The expression of p8 and p14 seems to be confined to a specific stage of myeloid cell differentiation, because both proteins are expressed in circulating neutrophils and monocytes but not in normal tissue macrophages. In chronic inflammatory conditions, however, such as rheumatoid arthritis, macrophages in affected tissues express both p8 and p14. These proteins are members of a family of CaBPs of low Mr, which include S-100 alpha and beta proteins, calcyclin (2A9), intestinal CaBP and p11. All the proteins have an Mr of approximately 10,000 with the exception of p14 which has a longer C-terminal sequence after the second calcium-binding domain. Little is known about their function, although by analogy with calmodulin they could be molecules involved in intracellular signalling that are activated by an increase in the intracellular Ca2+ concentration ([Ca2+]). Here we report that p14 is phosphorylated in both monocytes and neutrophils. The level of p14 phosphorylation can be increased by elevating the [Ca2+]i using the ionophore ionomycin, but is not affected by activation of protein kinase C using phorbol 12,13-dibutyrate. The phosphorylated residue is threonine at position 113, which is the penultimate amino acid in p14 and contained in the longer 'tail' sequence. Part of this sequence is identical to the neutrophil immobilizing factors NIF-1 and NIF-2, indicating that the phosphorylation event could have a role in the generation of NIF activity in the p14 protein.

Amino Acid Sequence↗

PubMed1989

Sequence identity.

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Amino Acid Sequence↗