The solution structure of oxidized Escherichia coli cytochrome b562.

The solution structure of the oxidized, paramagnetic form of cytochrome b562 from Escherichia coli (106 amino acids) is here reported as obtained from 1653 meaningful NOEs (from a total of 2051 unique NOEs), 33 (3)JHNHalpha values, and 339 pseudocontact shifts. The structure displays the typical four-helix bundle motif, and a disordered loop between helices alpha2 and alpha3, as found in the solid state. The solution structure has a conformation intermediate between the two independent solid-state molecules, although different orientations are observed for a few residues. The magnetic susceptibility tensor is similar to that of cytochrome c, which has the same ligands, although the anisotropy is somewhat smaller. This difference in the electronic structure is consistent with the thermal accessibility in cytochrome b562 of states with S > 1/2. The structure is also compared with the solution structure of the apoprotein, and some information on the role of the cofactor on the protein folding and mobility is obtained. Helix alpha4 seems to be the most sensitive to the chemical environment in terms of structure and mobility. The pKa values affecting the hyperfine-shifted signals are also discussed. Quite intriguing is the comparison of the structure of cytochrome b562 with the available structures of cytochromes c' which display a similar folding motif and similar pKa values but very little sequence similarity.     

The ATPase subunit 6 gene sequence predicts that RNA editing is conserved between lizard- and human-infecting Leishmania.

Here we investigate the similarities in the kinetoplastid RNA editing process between human- and lizard-infecting Leishmania species. We present the sequence of the maxicircle-encoded ATPase subunit 6 gene from L. (V.) panamensis, L. (L.) mexicana and L. (L.) donovani species of human-infecting Leishmania. These represent the first available sequences of this gene from Leishmania species other than the lizard-infecting L. tarentolae. The gene sequences are highly conserved, both over the edited and unedited parts of the gene, implying that the RNA editing process is likely to be highly conserved between Leishmania species. Indeed, the first editing domain is absolutely conserved in all three Leishmania species studied and L. tarentolae. A phylogeny based on part of the ATPase subunit 6 gene placed the lizard-infecting Leishmania within the monophyletic Leishmania genus, supporting previous data which suggest that lizard- and human-infecting Leishmania species are closely related.     

Still a puzzle: why is haem covalently attached in c-type cytochromes?

c-Type cytochromes are a group of proteins with diverse structures and functions. Their common feature is covalent attachment of haem to one or more CXXCH motifs. There does not seem to be a single advantageous reason for this covalent attachment.     

Peripheral plasma levels of progesterone in pregnant goats and in pregnant goats treated with prostaglandin F2a

Prostaglandin or prostaglandin analogues have been shown to be luteolytic in the pregnant goat. In this study the temporal changes in the plasma concentrations of progesterone during pregnancy and after administration of PGF2a to pregnant goats are described. PGF2a administration to pregnant goats at 30 and 65 days after breeding induced abortion within 34 to 75 hours. These abortions were accompanied by estrus and profuse muco-hemorrhagic discharges. When PGF2a was administered to pregnant goats 140 or 142 days after breeding, premature parturition occurred within 42 to 76 hours. Live kids were delivered in all cases. The plasma levels of progesterone in all pregnant goats showed dramatic decreases within 24 hours after the prostaglandin injections and continued to decrease gradually until abortions or premature parturition. Thereafter, the progesterone levels remained low for several days.     

Influence of Low Temperature on Development of Meloidogyne incognita and M. hapla Eggs in Egg Masses

Egg masses of Meloidogyne incognita and M. hapla were placed in soil at 10, 12, 16, and 20 C. At regular intervals, eggs from samples of egg masses were released from the gelatinous matrices and their developmental stages recorded. The number of days necessary to complete each stage from gastrulation to hatch is given for each temperature. The minimal temperature threshold for the development of eggs was computed by linear regression to be 8.26 C for M. incognita and 6.74 C for M. hapla.     

Activation by dopamine of patterned motor output from the buccal ganglia of Helisoma trivolvis

The buccal ganglia of the snail, Helisoma trivolvis, contain an intrinsic system of dopamine-containing neurons (Trimble, Barker, and Bullard, 1983). Dopamine, when bath applied to the isolated buccal ganglia, activates patterned motor output in a dose-dependent fashion. Haloperidol blocks the activating effect of dopamine, but the similar activation evoked by serotonin is not blocked by haloperidol. We suggest that there are two separate mechanisms for activating patterned motor output from the buccal ganglia. One is serotonergic, emanating from identified cerebral ganglion cells (Granzow and Kater, 1977), while the other is dopaminergic, involving neurons intrinsic to the buccal ganglia.     

Influence of Aldicarb on the Growth and Yield of Tobacco

Microplot and field experiments were used to examine the plant-growth stimulation frequently associated with the use of aldicarb on tobacco in the absence of major pests. Aldicarb rates of 1.5-4.5 kg a.i./ha enhanced tobacco growth and yield in most experiments, but higher rates (≥ 4.5 kg) usually resulted in a neutral to negative effect. Tobacco cultivars NC 82 and Speight G-28 were more responsive than McNair 944 to the pesticide in microplots. Supplemental irrigation enhanced the responsiveness of Speight G-70 tobacco and McNair 944 to aldicarb, but excessive moisture (ca. 7-8 cm/week) limited cured-leaf yields. Aldicarb also resulted in the greatest mean tobacco yields in 35 field experiments involving Meloidogyne spp. over 3 years, relative to ethoprop, 1,3-dichloropropene (1,3-D), 1,3-D + chloropicrin, and nontreated controls. Thus, aldicarb generally enhanced tobacco growth and yield in the presence or absence of nematodes, but its impact is dependent on other variables, including cultivar, soil moisture, and soil type.