Antiproliferative effect of the C-terminal fragments of parathyroid hormone-related protein,PTHrP-(107–111) and (107–139), on osteoblastic osteosarcoma cells

The C-terminal region of parathyroid hormone-related protein (PTHrP) containing the sequence (107–111) appears to be a potent inhibitor of osteoclastic bone resorption. In the present study, we have investigated the effect of human (h)PTHrP (107–139) and hPTHrP (107–111)NH₂ on the proliferation of osteoblastic rat osteosarcoma UMR 106 cells. We found that both C-terminal PTHrP peptides, like hPTHrP (1–141), were antimitogenic for these cells, between 1 pM and 10 nM. [Tyr³⁴]hPTHrP (1–34)NH₂ was as potent as these peptides but less effective as growth inhibitor in these cells. UMR 106 cells were found to produce and secrete immunoreactive PTHrP. Addition of anti-PTHrP neutralizing antibodies to C- and N-terminal epitopes of PTHrP increased the growth of these cells. Our data suggest that the antiproliferative effect of these C-terminal PTHrP analogs may be independent of cyclic adenosine 3′:5′-monophosphate (cAMP) and mediated by protein kinase C. These findings support an autocrine role of PTHrP in bone metabolism. J. Cell. Physiol. 170:209–215, 1997. © 1997 Wiley-Liss, Inc.     

Estimating domain orientation of two human antibody IgG4 chimeras by crystallohydrodynamics

A modified crystallohydrodynamic approach introduced in 2001 is applied to two human IgG4 constructs from mouse IgG1. The constructs were point mutants of the chimeric antibody molecule cB72.3(4): cB72.3(4A), devoid of inter-chain disulfide bridging, and cB72.3(4P), which has full inter-chain bridging. As before, the known crystallographic structures for the Fab and Fc domains were combined with the measured translational frictional ratios to obtain an estimate for the apparent time-averaged hydration of the domains and hence for that of the intact molecule. The original approach was modified with the hydrated dimensions of the domains being applied, rather than the anhydrous crystallographic dimensions, for assessing the inter-domain orientations using the algorithms HYDROSUB and SOLPRO. Both chimeric IgG4 molecules were found to have open, rather than compact, structures, in agreement with the previous study on wild-type human IgG4. The insertion of a frictionless connector between the domains was necessary, however, for representing the cB72.3(4A) chimera. It therefore appears that the inter-chain disulfide bonds act as physical constraints in the cB72.3(4P) chimera, forcing the antibody domains together and producing a less elongated structure than that of cB72.3(4A). The open structures produced for the two IgG4 chimeras showed similarity to those structures identified for murine IgG1 and IgG2a molecules through X-ray crystallography.Presented at the conference for Advances in Analytical Ultracentrifugation and Hydrodynamics, 8–11 June 2002, Grenoble, France     

A new species and two new combinations of Leontodon (Asteraceae, Hypochoeridinae)

Leontodon palisiae sp. nov. occurring in the Iberian Peninsula, Morocco and the Canary Islands is described and illustrated. Cytological data as well as some preliminary results of self-incompatibility tests in L. palisiae are presented. A comparative carpological study of L. muelleri, L. palisiae and L. salzmannii using the SEM is made, and an identification key of these three species is provided. Two new combinations, L. muelleri ssp. trivialis comb. nov., from Morocco, and L. kralikii comb. nov., from Libya and Tunisia, are proposed. All taxa belong to the series Annui of sect. Kalbfussia in subgenus Oporinia. The basic chromosome number x=5 is here reported for the first time within the genus.     

Conserved asparagine residue 54 of alpha-sarcin plays a role in protein stability and enzyme activity

Asparagine 54 of alpha-sarcin is a conserved residue within the proteins of the ribotoxin family of microbial ribonucleases. It is located in loop 2 of the protein, which lacks repetitive secondary structure elements but exhibits a well-defined conformation. Five mutant variants at this residue have been produced and characterized. The spectroscopic characterization of these proteins indicates that the overall conformation is not changed upon mutation. Activity and denaturation assays show that Asn-54 largely contributes to protein stability, and its presence is a requirement for the highly specific inhibitory activity of these ribotoxins on ribosomes.