PubMed · 124547
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I Zabin, M R Villarejo. 1975. Protein complementation.. https://doi.org/10.1146/annurev.bi.44.070175.001455
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Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus, the two most abundant phototrophs on Earth, thrive in oligotrophic oceanic regions. While it is well known that specific lineages are exquisitely adapted to prevailing in situ light and temperature regimes, much less is known of the molecular machinery required to facilitate occupancy of these low-nutrient environments. Here, we describe a hitherto unknown alkaline phosphatase, Psip1, that has a substantially higher affinity for phosphomonoesters than other well-known phosphatases like PhoA, PhoX, or PhoD and is restricted to clade III Synechococcus and a subset of high light I-adapted Prochlorococcus strains, suggesting niche specificity. We demonstrate that Psip1 has undergone convergent evolution with PhoX, requiring both iron and calcium for activity and likely possessing identical key residues around the active site, despite generally very low sequence homology. Interrogation of metagenomes and transcriptomes from TARA oceans and an Atlantic Meridional transect shows that psip1 is abundant and highly expressed in picocyanobacterial populations from the Mediterranean Sea and north Atlantic gyre, regions well recognized to be phosphorus (P)-deplete. Together, this identifies psip1 as an important oligotrophy-specific gene for P recycling in these organisms. Furthermore, psip1 is not restricted to picocyanobacteria and is abundant and highly transcribed in some α-proteobacteria and eukaryotic algae, suggesting that such a high-affinity phosphatase is important across the microbial taxonomic world to occupy low-P environments.
The effect of human interleukin-4 (hIL-4) on mineralization in human osteoblast-like cells was investigated. Confluent cells were incubated with hIL-4 for 16 or 30 days in the presence or absence, respectively, of alpha-glycerophosphate (alpha-GP), which accelerates the mineralization process. hIL-4 (0.3 ng/ml) induced mineralization with 1.9-, 26- and 37-fold increases of hydroxyproline, calcium, and osteocalcin content, respectively, in the presence of alpha-GP. Mineralization was not induced with other cytokines, hIL-1, hIL-2, hIL-6, or mIL-4. hIL-4 also induced mineralization in the absence of alpha-GP in a manner different from that of 1 alpha, 25(OH)2 vitaminD3 (1,25(OH)2VD3). These findings suggest that IL-4 may play an important role in bone formation.
A new radioimmunoassay for p53, employing an anti-peptide antibody directed against conserved Domain V, exhibited specificity for a relatively dephosphorylated form of p53. This form, correlated with the monoclonal antibody PAB421+ conformation, appeared transiently in the cytosol of cycloheximide-treated T cells undergoing activation by concanavalin-A/serum. Concurrently, there were decreased levels of p53 in the nucleus that correlated with increased phosphorylation of p53. After 90 min nuclear levels of p53 increased steadily above levels of unstimulated cells. Anti-p53 antibodies introduced into cells prior to stimulation enhanced cell proliferation in response to mitogens.