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101.
Alicia Mimbrera Luis Rivas Faustino Mollinedo Emilio Muñoz Vicente Larraga 《Molecular and cellular biochemistry》1983,56(1):73-80
Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [125I] applied to membrane-bound or soluble pure F1-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F1-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F0 component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry 3 3 2 2 (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein. 相似文献
102.
103.
104.
Tubular Transport Maxima of PAH and Diodrast Measured Individually in the Aglomerular Kidney of Lophius, and Simultaneously as Competitors Under Conditions of Equimolar Loading
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![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The maximal tubular transfer rates (Tm) of both p-aminohippurate (PAH) and diodrast (3,5-diiodo-4-pyridone-N-acetic acid or iodopyracet) were found to be fixed and reproducible when measured separately in Lophius (goosefish) under standard laboratory conditions. Expressed on a molar basis TmPAH was four times TmD. However, when these transport competitors were presented simultaneously in equimolar concentrations with the plasma levels of each sufficiently high enough to saturate the carrier system, the relative rates of excretion were reversed with the diodrast transfer rate then four times that of PAH. The combined rate of excretion was far below TmPAH alone, and roughly equal to TmD. Interaction with a common carrier was indicated by the gradations in degree of inhibition which resulted when plasma concentration ratios of diodrast to PAH were extended from 0.1 to 3.2, and PAH transfer rates expressed as percentage of TmPAH were correspondingly depressed from 17 to 1.0 per cent respectively. These observations again point up the inverse relationship between transfer rate and competitive effectiveness which exists for members of a series of substances actively transported by a common mechanism. It appears that carrier affinity and dissociation characteristics may be quite different for various compounds in a series, and also that these parameters may vary significantly from species to species. 相似文献
105.
106.
Morphological comparisons are made from the study of 64 specimens belonging to the following species:Squalus acanihias, S. blainvillei, S. megalops andS. acutirostris. The results suggest conspecificity betweenS. acutipinnis andS. megalops. The differences betweenS. blainvillei andS. megalops in the E-Atlantic are stressed. The Indo-Pacific species calledS. blainvillei by Chen et al. (1979) is regarded in this paper as probably an undescribed species. Some consideration on the status of several nominal species and the species grouping withinSqualus are also made. 相似文献
107.
108.
Molecular dissection of the NH2-terminal signal/anchor sequence of rat dipeptidyl peptidase IV 总被引:7,自引:3,他引:4
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![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dipeptidyl peptidase IV (DPPIV) is a membrane glycoprotein with a type II orientation in the plasma membrane. As shown in a cell-free translation system, the amino-terminal 34 amino acids of rat DPPIV are involved in translocating nascent polypeptide across the membrane of microsomes and in anchoring the translocated polypeptide in the microsomal membrane. The amino-terminal sequence performing this dual function is composed of: a central hydrophobic core of 22 amino acid residues; 6 amino-terminal residues preceding the hydrophobic core (MKTPWK); and 6 residues following the hydrophobic core. The six residues preceding the hydrophobic core are exposed on the outside (cytoplasmic side) of the microsomal membrane. Site-directed mutagenesis studies show that deletion of this cytoplasmic domain, excluding the amino-terminal initiating methionine, does not affect translocation of nascent DPPIV polypeptide, but does affect significantly anchoring of the translocated polypeptide in the microsomal membrane. In contrast, changing the two cytoplasmic Lys to Glu residues or shortening of the hydrophobic core from 22 to 15 residues or converting the last 11e of the shortened hydrophobic core into Ala affects neither translocation across nor anchoring of the DPPIV polypeptide in the microsomal membrane. These and other structural features of the DPPIV amino-terminal signal-anchor sequences are discussed along with other types of sequences for their role in targeting nascent polypeptides to the RER. 相似文献
109.
K C Wang S Huh S T Hong J Y Chai K S Choi S H Lee 《The Korean journal of parasitology》1990,28(1):1-10
To establish an animal model of intracranial sparganosis, the fate and behavior of the experimentally inoculated spargana were observed. A total of 102 scolices of spargana were injected into 22 cat brains, and the cats were sacrificed at 2 weeks, 1 month, 3 months and 6 months after the inoculation. Neurosparganosis was established in 77% of the cats. Of 43 recovered worms, 19 (44%) were located in the subdural or subarachnoid space, 16 (37%) in the brain parenchyme, and 2 (5%) in the lateral ventricle. One was detected at the diploic space of the skull and 5 were outside the cranial cavity. All but one were alive, and had grown tails. They were distributed in the brain parenchyme randomly. There was no place which they could not invade. No adult was found in the intestine. Cerebrospinal fluid (CSF) was collected before inoculation, 1 week, 2 weeks, 1 month, 3 months and 6 months after inoculation. The level of anti-sparganum IgG antibody in CSF measured by ELISA began to increase above the criteria of positivity 1 month after inoculation. Three months after inoculation, the values markedly increased. The present findings reveal that intracranial inoculation of spargana into the brains of cats would be a good animal model of experimental neurosparganosis. 相似文献
110.
Q C Shen V Simplaceanu P F Cottam J L Wu J S Hong C Ho 《Journal of molecular biology》1989,210(4):859-867
The results of molecular genetic, biochemical and nuclear magnetic resonance studies on glutamine-binding protein of Escherichia coli suggest that the only two tryptophan residues, at positions 32 and 220, in the protein molecule are likely to be involved in (or sensitive to) interactions with the membrane-bound protein components of the glutamine transport system. It has been found that both tryptophan residues have limited motional freedom, are located away from the surface of the protein molecule and are not close to the ligand-binding site. Their presence, however, is required for the optimal transport of L-glutamine across the cytoplasmic membrane, though not essential for the ligand-binding process. The relevance of these results to the structure and function of the glutamine-binding protein in the glutamine transport system is discussed. 相似文献