Purification of a WD repeat protein, EMAP, that promotes microtubule dynamics through an inhibition of rescue

The major microtubule-associated protein in echinoderms is a 77-kDa, WD repeat protein, called EMAP. EMAP-related proteins have been identified in sea urchins, starfish, sanddollars, and humans. We describe the purification of sea urchin EMAP and demonstrate that EMAP binding to microtubules is saturable at a molar ratio of 1 mol of EMAP to 3 mol of tubulin dimer. Unlike MAP-2, MAP-4, or tau proteins, EMAP binding to microtubules is not lost by cleavage of tubulin with subtilisin. In addition to binding to the microtubule polymer, EMAP binds to tubulin dimers in a 1:1 molar ratio. The abundance of EMAP in the egg suggests that it could function to regulate microtubule assembly. To test this hypothesis, we examined the effects of EMAP on the dynamic instability of microtubules nucleated from axoneme fragments as monitored by video-enhanced differential interference contrast microscopy. Addition of 2.2 microM EMAP to 21 microM tubulin results in a slight increase in the elongation and shortening velocities at the microtubule plus ends but not at the minus ends. Significantly, EMAP inhibits the frequency of rescue 8-fold without producing a change in the frequency of catastrophe. These results indicate that EMAP, unlike brain microtubule-associated proteins, promotes microtubule dynamics.     

Decreased survival in patients with co-existent rheumatoid arthritis and bronchiectasis

The aim was to compare the 5 yr survival in patients with rheumatoid arthritis (RA) alone, bronchiectasis (Br) alone and RA plus Br (RA-Br). A case-control study was carried out in which 32 patients with RA-Br were matched for age (within 5 yr), sex and (where possible) disease duration with 32 patients with RA alone. An additional comparison group of 31 unselected patients with Br was chosen. All patients were followed for 5 yr. Patients with RA-Br were 7.3 times more likely to die than the general population, 5.0 times more likely than the RA group and 2.4 times more likely than the Br group. An increased risk of death within the RA-Br group was associated with a history of smoking, more severe RA and steroid usage. The co-existence of RA and Br is associated with a poor 5 yr survival.     

Blue-green algae: their excretion of iron-selective chelators enables them to dominate other algae

During blue-green algal blooms, other algae can be completely suppressed. This ability of blue-green algae to suppress other algae may be determined by the abailability of iron. Iron deprivation induces the production of hydroxamate chelators, which appear to be the agent suppressing other algae.