Sequence homology of the Ca2+-dependent regulator of cyclic nucleotide phosphodiesterase from rat testis with other Ca2+-binding proteins.

A Ca2+-dependent regulator protein of cyclic 3':5'-nucleotide phosphodiesterase (EC 3.1.4.17) has previously been isolated from rat testis and shown to be a heat-stable, Ca2+-binding protein with a molecular weight of approximately 17,000. The Ca2+-dependent regulator protein is also structurally similar to troponin-C, the Ca2+-binding component of muscle troponin and Ca2+ mediator of muscle contraction. The present report describes a partial amino acid sequence of the Ca2+-dependent regulator. The protein (148 amino acids) is 50% homologous with skeletal muscle troponin-C, but is 11 residues shorter than the muscle protein. The Ca2+-dependent regulator protein has an NH2-terminal sequence of acetyl-Ala-Asp-Glu, a COOH-terminal sequence of Thr-Ala-Lys and 1 residue of epsilon-trimethyllysine located at position 115. All of these properties are distinct from those of other homologous Ca2+-binding proteins. These properties may account for the biological specificities demonstrated by these proteins as compared to the Ca2+-dependent regulator protein. Based on the sequence and a comparison of the Ca2+-dependent regulator protein to other calcium-binding proteins, our data support the view that all of these moecules contain common sequences, especially at their proposed metal-binding sites.     

Gigantic mammary hyperplasia in pregnancy associated with pseudohyperparathyroidism

This is the first report of hypercalcemia due to benign gigantic mammary hyperplasia in a pregnant women. Endocrinologic examinations did not disclose any known cause for the symptomatic hypercalcemia. Bilateral total mastectomy decreased the serum calcium level to normal. The case is presented with discussion and a literature review.     

Ras regulatory interactions: Novel targets for anti-cancer intervention?

Advances in the understanding of Ras oncoprotein function suggest novel points for anti-tumor intervention. First, upstream-acting guanine nucleotide exchange factors and SH2/SH3 domain-containing adaptor proteins that link Ras with growth factor receptor tyrosine kinases have recently been characterized. Second, work on downstream-acting Ras effector functions including the Ras GTPase-activating protein (p120^GAP) and the Raf kinase has revealed direct biochemical interactions that are functionally required for oncogenic Ras signalling. We summarize progress in these areas and discuss the potential for novel applications to anti-cancer chemotherapy.     

A novel approach to the isolation of rabbit reticulocyte haem-controlled eIF-2α protein kinase

A new strategy for the purification of rabbit reticulocyte haem-controlled eIF-2α kinase is described, based on the fact that this kinase can be self-phosphorylated in several sites. Incubation of partially purified kinase with ATP changes its behaviour on anion exchangers sufficiently to separate it from almost all contaminating proteins.