Metallocluster extrusion requirements, interspecies MoFe-protein primary sequence comparisons and comparison of the primary sequences of the MoFe-protein subunits with each other have been used to assign potential P-cluster (Fe-S cluster) domains within the MoFe protein. In each alpha-beta unit of the MoFe protein, alpha-subunit domains, which include potential Fe-S cluster ligands Cys-62, His-83, Cys-88 and Cys-154, and beta-subunit domains, which include potential Fe-S cluster ligands Cys-70, His-90, Cys-95 and Cys-153, are proposed to comprise nearly equivalent P-cluster environments located adjacent to each other in the native protein. As an approach to test this model and to probe the functional properties of the P clusters, amino acid residue substitutions were placed at the alpha-subunit Cys-62, His-83, Cys-88 and Cys-154 positions by site-directed mutagenesis of the Azotobacter vinelandii nifD gene. The diazotrophic growth rates, MoFe-protein acetylene-reduction activities, and whole-cell S = 3/2 electron paramagnetic resonance spectra of these mutants were examined. Results of these experiments show that MoFe-protein alpha-subunit residues, Cys-62 and Cys-154, are probably essential for MoFe-protein activity but that His-83 and Cys-88 residues are not. These results indicate either that His-83 and Cys-88 do not provide essential P-cluster ligands or that a new cluster-ligand arrangement is formed in their absence. 相似文献
A soluble extract was obtained on treatment of rat liver mitochondrial outer membranes with cholate which bound [14C]malonyl-CoA but was essentially free of carnitine palmitoyltransferase (CPT) activity. Extraction of mitochondrial inner membranes with cholate readily solubilized a CPT activity which was insensitive to malonyl-CoA. Combination of these two extracts caused the CPT derived from inner membranes to become inhibitable by malonyl-CoA. 相似文献
The presence of G-proteins in the eyespot fraction of Chlamydomonas reinhardtii is shown. This fraction is capable of binding (GTPγ[35S], possesses the GTPase activity and interacts with antibodies raised against a highly conserved peptide of most G-proteins' -subunit. Cross-reaction with a 24-kDa protein is detected on immunoblots. Using an antiserum prepared from vertebrate β-subunit peptide, two additional proteins with apparent Mr 21 and 29 kDa could be revealed. The light-dependence of GTPase extraction from eyespot membranes is shown. The results make it possible to suggest the participation of G-proteins in the photosensory transduction chain of Ch. reinhardtii. 相似文献
A dominant mutation, responsible for the resistance to oxythiamin inSaccharomyces cerevisiae was mapped on the right arm of chromosome IV, 4.6 cM centromere-distally totrp1. The corresponding gene is not involved in the control of intracellular content of total thiamin during growth on a minimal
medium without thiamin. 相似文献
More than 40 mostly minor Palaeozoic oolitic ironstones (OI) accumulated on low-latitude cratonic North America, almost entirely in USA. A few Middle Cambrian OI, among the oldest anywhere, were deposited on the western cratonic shelf of USA. Widely scattered Late Cambrian ones developed on the southwestern, southeastern and northeastern flanks of the Transcontinental Arch. Middle Ordovician OI were deposited on the cratonic interior and on the southern and southeastern cratonic margins. In latest Ordovician time Neda OI spread across north-central USA east of the Arch and south of the Laurentian upland. Minor ones developed in the southern part of the Taconian foreland basin after major orogeny. Early and Middle Silurian Clinton OI flourished throughout the foreland basin in eastern USA, producing the largest OI deposit on the North American craton. Minor early Late Silurian OI accumulated in the central part of the basin. Middle and Late Devonian OI in the Acadian foreland basin in northeastern cratonic USA developed progressively westward of the encroaching Catskill delta. An isolated Middle Devonian one accumulated in southwestern cratonic USA, and latest Devonian ones in north-central USA east of the Arch.
During this Palaeozoic episode sites of OI deposition shifted eastward across the craton. Most of the OI were deposited during a hiatus in normal sedimentation, accumulating in the upper part of shoaling-upward sequences. Some early Palaeozoic ones occur in glauconitic siliciclastic-carbonate facies and contain mostly spherical hematitic ooids. These suggest derivation from iron-rich soils developed on glauconitic deposits. OI in wholly siliciclastic facies, containing distorted chamositic ooids with cores of mud peloids, were common in later Palaeozoic time. These OI, like many other Phanerozoic ones, suggest a synsedimentary to early diagenetic origin. 相似文献
A covalent cross-linking technique was used to bind iodinated interleukin-1 (IL1) alpha and beta to plasma proteins. One specific IL1 beta binding protein was observed, that when cross-linked to 125I-ILl beta migrated to approximately 60 kDa on SDS-PAGE. The protein did not bind IL1 alpha. The 43 -kDa protein was partially purified using a wheat germ agglutinin affinity column. The isolated factor again specifically bound IL1 beta, and appeared to consist of single chain glycoprotein. The protein was heat stable and had a rapid association time with IL1 beta. This protein may be an important carrier molecule for IL1 beta in vivo. 相似文献
The presence of the egg size-determining (Esd) gene, which acts as a quantitative gene, on the W chromosome of the silkworm was revealed in a previous study by using two types of triploid females, ZZW and ZWW, (Kawamura, Genetica 76: 195–201). The females with the sex-linked giant egg (Ge) gene deposit eggs as large as those laid by tetraploids. If the Ge mutant is induced by translocation of a fragment of the W carrying Esd onto the Z by chance, the egg size increase in the Ge strain and in tetraploids may be easily explained by the double dose of Esd. The measurement of the length of the Z-W bivalent in oocytes showed that the Z of the Ge strain was much longer than that of the other strains which do not carry the Ge gene. The result suggests that the Ge gene is identical with the Esd on the W chromosome of the silkworm. 相似文献
Changes in respiratory mechanical loads are readily detected by humans. Although it is widely believed that respiratory muscle afferents serve as the primary source of information for load detection, there is, in fact, no convincing evidence to support this belief. We developed a shell that encloses the body, excluding the head and neck. A special loading apparatus altered pressure in proportion to respired volume (elastic load) in one of three ways: 1) at the mouth only (T), producing a conventional load in which respiratory muscles are loaded and airway and intrathoracic pressures are made negative in proportion to volume, 2) both at the mouth and in the shell (AW), where the same pattern of airway and intrathoracic pressure occurs but the muscles are not loaded because Prs (i.e., mouth pressure minus pressure in the shell is unchanged, and 3) positive pressure in proportion to volume at the shell only, loading the chest wall but causing no change in airway or thoracic pressures (CW). The threshold for detection (delta E50) with the three types of application was determined in seven normal subjects: 2.16 +/- 0.22, 2.65 +/- 0.54, and 6.21 +/- 0.85 (SE) cmH2O/l for T, AW, and CW, respectively. Therefore the active chest wall, including muscles, is a much less potent source of information than structures affected by the negative airway and intrathoracic pressure. The latter account for the very low threshold for load detection. 相似文献
Viable yellow obese mice (Avy/a) were treated for 10 days with 5, 15, 50 or 150 micrograms/d of either alpha-MSH or desacetyl-MSH. The half-maximal effect on weight gain occurred with a dose of 5 micrograms/d for desacetyl-MSH and at a 30 fold higher level of 150 micrograms/d for alpha-MSH. In contrast, the half-maximal stimulation of eumelanin production by alpha-MSH occurred at 15 micrograms/d and with desacetyl-MSH at 150 micrograms/d, a 10-fold increase. Desacetyl-MSH produced a dose-related increase in the weight of muscle, as well as white and brown adipose tissue. Desacetyl-MSH and alpha-MSH both increased plasma corticosterone concentrations, but desacetyl-MSH was more potent. In a 2 x 2 factorial designed study, body weight was significantly increased in viable yellow mice only by treatment with desacetyl-MSH but in the lean animals, both alpha-MSH and desacetyl-MSH increased body weight. Food intake was significantly different between genotypes, and was stimulated by desacetyl-MSH. These studies demonstrate potent differences in biological actions on food intake, body weight, and a variety of organ weights between acetylated and desacetylated forms of MSH. 相似文献