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PubMed1976

Ceruloplasmin: the copper transport protein with essential oxidase activity.

Ceruloplasmin, the blue copper-protein of vertebrate plasma, has been reviewed mainly from a functional point of view. However we have surveyed the chemistry and state copper in the molecule because of the implications of the recent data of Ryden (13,28). His observations suggest that unless special precautions are taken in the isolation of ceruloplasmin degradation, probably proteolytic, produces fragments of various sizes. When isolated, these fragments appear to be held together by noncovalent interactions. Comparison of their catalytic and spectral properties reveals no significant differences from a single homogeneous species of molecular weight of 134,000 isolated by Ryden's methods. On the other hand, the homogeneous molecule may differ in properties highly sensitive to conformation and three-dimensional parameters. Three types of copper atoms have been identified in ceruloplasmin, but their amino acid environment is still unknown. Ceruloplasmin possesses significant oxidase activity towards Fe(II) and numerous aromatic amines and phenols. Its ferroxidase activity has led to the discovery that it is a molecular link between copper and iron metabolism. Ceruloplasmin mobilizes iron into the plasma from iron storage cells in the liver. An equally important duty is that ceruloplasmin, after its rapid biosynthesis in the liver, serves as a major copper transport vehicle, comparable to transferrin. Evidence is accumulating that the copper atoms of ceruloplasmin are a prerequisite for copper utilization in the biosynthesis of cytochrome oxidase and other copper proteins. The ability of ceruloplasmin to release copper at specific cellular sites may be related to its broad substrate spectrum of biological reducing agents. A possible third role of ceruloplasmin is as a contributor to the regulation of the balance of biogenic amines through its oxidase action on the epinephrine and the hydroxyindole series. Thus ceruloplasmin is a copper-protein with several important functions, all of which are directly related to its oxidase activity.

Animals↗
PubMed1973

The origin of life.

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Biochemical Phenomena↗
PubMed1997

Selective compartments for resistant microorganisms in antibiotic gradients.

The development of bacterial resistance to antibiotics is one of the best documented examples of contemporary biological evolution. Variability in the mechanisms of resistance depends on the diversity of genotypes in the huge bacterial populations, and also on the diversity of selective pressures that are produced along the antibiotic concentration gradients formed in the highly compartmentalized human body during therapy. These antibiotic gradients can be conceived as comprising selective compartments, each one of them defined as the concentration able to select a particular genetic variant. In vitro experimental models confirm that some antibiotic resistant variants are selected only at certain selective concentrations of antibiotics. The correspondence between selective compartments and selectable variants could offer a way of describing more accurately the antibiotic selective landscapes and for taking measures to prevent the development of a major threat to the future of modern medicine.

Anti-Bacterial Agents↗
PubMed2006

The origin of the diversity of leaf venation pattern.

The leaf venation pattern of plants shows remarkable diversity and species-specificity. However, the mechanism underlying the pattern formation and pattern diversity remains unclear. We developed a mathematical model that is based on the positive feedback regulation between plant hormone auxin and its efflux carrier. This system can generate auxin flow pathways by self-organization from an almost homogeneous state. This result explains a well-known experimental phenomenon referred as to "polar auxin transport." The model can produce diverse leaf venation patterns with spatial regularity under similar conditions to those of leaf development, that is, in the presence of leaf expansion and auxin sink. Final venation patterns are strikingly affected by leaf shape and leaf expansion. These results indicate that the positive feedback regulation between auxin and its efflux carrier is a central dynamic in leaf venation pattern formation. The diversity of leaf venation patterns in plant species is probably due to the differences of leaf shape and leaf expansion pattern.

Algorithms↗
PubMed1993

Yeast syntaxins Sso1p and Sso2p belong to a family of related membrane proteins that function in vesicular transport.

The yeast SEC1 gene encodes a hydrophilic protein that functions at the terminal stage in secretion. We have cloned two yeast genes, SSO1 and SSO2, which in high copy number can suppress sec1 mutations and also mutations in several other late acting SEC genes, such as SEC3, SEC5, SEC9 and SEC15. SSO1 and SSO2 encode small proteins with N-terminal hydrophilic domains and C-terminal hydrophobic tails. The two proteins are 72% identical in sequence and together perform an essential function late in secretion. Sso1p and Sso2p show significant sequence similarity to six other proteins. Two of these, Sed5p and Pep12p, are yeast proteins that function in transport from ER to Golgi and from Golgi to the vacuole, respectively. Also related to Sso1p and Sso2p are three mammalian proteins: epimorphin, syntaxin A/HPC-1 and syntaxin B. A nematode cDNA product also belongs to the new protein family. The new protein family is thus present in a wide variety of eukaryotic cells, where its members function at different stages in vesicular transport.

Amino Acid Sequence↗
PubMed2003

Mechanisms and functional aspects of intestinal calcium absorption.

Calcium absorption, in terms of mechanisms and function, is well adapted to meet the calcium needs of mammals. When calcium levels in the food are low, the active, mediated transcellular calcium transport assumes primary importance. This process is vitamin D-dependent, largely localized in the duodenum, and involves three steps: entry across the brush border, mediated by a molecular structure, CaT1, with two components; a facilitated transport that saturates at low luminal calcium concentration; and a channel component through which most calcium enters the cell at the higher luminal concentrations. Intracellular diffusion is assured by a small, cytosolic calcium binding molecule, calbindinD(9k), which carries more than 90% of the calcium that traverses the duodenal cell, thus also serving as a buffer. Extrusion is by the CaATPase and is not a limiting step. Calcium entry is reduced by more than 90% in the absence of vitamin D, with biosynthesis of calbindinD(9k) totally vitamin D-dependent. Active transport is upregulated on low calcium intake and downregulated at high calcium intake, when paracellular calcium transport through the tight junctions of the intestine becomes the dominant process. The amount of calcium absorbed paracellularly is a function of the calcium gradient between lumen and plasma and of the time the chyme spends at a given intestinal site. The coexistence of mediated and nonmediated transport processes assures the organism of an adequate calcium supply, yet prevents excessive calcium absorption.

Absorption↗
PubMed2005

Extensive enlargement of the maxillary sinus in Alouatta caraya (mammalia, primates, cebidae): an allometric approach to skull pneumatization in Atelinae.

In contrast to the paranasal sinuses of Old World monkeys and hominoids, little information is available about the paranasal sinuses of New World monkeys. Because this information is crucial in order to draw further conclusions about the evolution and biological role of skull pneumatization, this study investigates the morphology of the paranasal sinuses in adult black-and-gold howler monkeys (Alouatta caraya). Volumes of the paranasal sinuses were calculated using computer software (SURFdriver or Allegro) from serial coronal CT scans of 20 skulls of both sexes. Skull pneumatization in A. caraya is more complex than in other higher primates. In both sexes, the maxillary sinus (MS) is the only pneumatic cavity and enlarges regularly into neighboring bones such as the frontal bone and the basisphenoid. The resulting pansinus is often partitioned by several vertical septa. As in most external cranial dimensions, mean MS volume of A. caraya (male 4.08 cm(3); female 2.00 cm(3)) shows significant sexual dimorphism. Reduced major axis regression analysis between MS volume and different cranial dimensions for A. caraya (and for available data from other platyrrhines) suggests a distinct association for this group, with Alouatta having one of the largest pneumatic cavities. The combination of this unusual expansion of the MS of Alouatta and the occurrence of distinct septa within the sinus may be a consequence of the distinct skull architecture of Alouatta.

Alouatta↗
PubMed1992

A new subfamily of bacterial ABC-type transport systems catalyzing export of drugs and carbohydrates.

Sequence comparison studies revealed that the drug resistance transporter of Streptomyces peucetius (DrrAB) and two nodulation gene products (NodIJ) of Rhizobium leguminosarum are homologous to proteins encoded by three sets of genes that comprise capsular polysaccharide export systems in gram-negative bacteria: KpsTM of Escherichia coli, BexABC of Haemophilus influenzae, and CtrDCB of Neisseria meningitidis. These five systems comprise a new subfamily within the family of ATP binding cassette (ABC)-type transporters. We have termed this subfamily the ABC-2 subfamily. For three of the systems comprising this subfamily (Drr, Nod, and Kps) only one integral membrane constituent has been identified, whereas for the other two systems (Bex and Ctr) two dis-similar integral membrane constituents have been found. This observation suggests that the transmembrane channels of ABC-2-type transporters can be formed of homo- or heterooligomers as is true of several other classes of transport systems.

Adenosine Triphosphate↗
PubMed1993

Secondary structural features of modules M2 and M3 of barnase in solution by NMR experiment and distance geometry calculation.

Proteins consist of structural units such as globular domains, secondary structures, and modules. Modules were originally defined by partitioning a globular domain into compact regions, each of which is a contiguous polypeptide segment having a compact conformation. Since modules show close correlations with the intron positions of genes, they are regarded as primordial polypeptide pieces encoded by exons and shuffled, leading to yield new combination of them in early biological evolution. Do modules maintain their native conformations in solution when they are excised at their boundaries? In order to find answers to this question, we have synthesized modules of barnase, one of the bacterial RNases, and studied the solution structures of modules M2 (amino acid residues 24-52) and M3 (52-73) by 2D NMR studies. Some local secondary structures, alpha-helix, and beta-turns in M2 and beta-turns in M3, were observed in the modules at the similar positions to those in the intact barnase but the overall state seems to be in a mixture of random and native conformations. The present result shows that the excised modules have propensity to form similar secondary structures to those of the intact barnase.

Amino Acid Sequence↗