Purification and immunocytochemical localization of kafirins inSorghum bicolor (L. Moench) endosperm

Summary Kafirins are the storage proteins of sorghum and are found in protein bodies in the seed endosperm. They have been classified as -, -, and -kafirins according to differences in molecular weight, solubility, and structure. The kafirins were purified, amino acid composition was determined, and immunolocalization methods were used to determine the organization of the protein bodies and distribution of kafirins throughout the endosperm. All three groups of kafirins were low in lysine. -Kafirins and -kafirins were relatively high in cysteine, and -kafirins were relatively high in methionine. Transmission electron microscopy showed that protein bodies in the peripheral endosperm were spheroid with concentric rings and few darkly stained inclusions. In contrast, protein bodies of the central endosperm were irregularly shaped with a higher proportion of darkly stained material. The light staining regions of the protein bodies are composed primarily of -kafirins with minor portions of - and -kafirins. The dark staining regions, however, are composed primarily of - and -kafirins. Immunoelectron microscopy showed that protein bodies in the peripheral endosperm contain predominantly a-kafirin with minor amounts of - and -kafirin. Central endosperm protein bodies are also predominantly -kafirin, but have a higher proportion of -kafirin and -kafirin than the peripheral endosperm protein bodies.Abbreviations GAR-HRP Goat anti-rabbit horseradish peroxidase - IgG immunoglobulin G - 2-ME 2-mercaptoethanol - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TBS Tris buffer saline - TBS-T Tris buffer saline with Tween - TBS-T-B Tris buffer saline with Tween and bovine serum albumin - TCA trichloroacetic acid - UV ultraviolet     

Zur Paarbildung der Uferschwalbe (Riparia riparia)

Zusammenfassung Uferschwalben kehren aus den afrikanischen Winterquartieren in Trupps beiderlei Geschlechts zurück. Erste Beringungsergebnisse belegen, daß zunächst mehrjährige, vermutlich untereinander bekannte Vögel eintreffen, die den Brutplatz aus vergangenen Brutperioden her kennen. Die Masse der später ankommenden Vögel dürfte weitgehend aus einjährigen oder ortsfremden Uferschwalben bestehen, die sich größtenteils erst während der Paarbildung persönlich kennenlernen. Der anfängliche Schwarmzusammenhalt der nacheinander eintreffenden Trupps führt zur Bildung von Subkolonien, die für Brutplätze ab einer bestimmten Größenordnung typisch sind. Uferschwalben- gründen nacheinander mehrere Reviere, d. h. sie besetzen Steilwandbereiche, in denen sie ausschließlich mit den Füßen eine Röhre oder Mulde graben, singen und Bogenflüge starten. Bis auf singende oder bekannte werden Artgenossen im Revier geduldet. Uferschwalben- suchen besetzte Reviere auf. Ohne Röhrenbindung verhalten sie sich still und unauffällig, ihre Grabungsaktivitäten sind von untergeordneter Bedeutung. Die Bindung an ein bestimmtes Revier entwickelt sich individuell verschieden und entscheidet über den Abschluß des Röhrenbaues (Herstellung der Nistkammer). Reviere ohne dauerhafte -Bindung werden von den aufgegeben. Aktivitäten, die auf wachsende Revierbindung eines hindeuten, sind: häufige oder/und länger dauernde Aufenthalte des in einem besetzten Revier und sporadisches Mitgraben; aggressives Verhalten gegenüber Artgenossen (i. d. R. fremde ), die im Revier landen wollen; gemeinschaftlicher, leiser Gesang von und im Röhrenbereich. Aktivitäten, die für eine vollzogene Paarbildung sprechen, sind: Fertigstellen der Röhre durch Grabung der Nestkammer; längere gemeinsame Aufenthalte innerhalb und außerhalb der Röhre; Voranfliegen des beim Röhrenanflug; Übernachten von und in der Röhre; Nestbau; ausdauernde Verfolgungsflüge während der Kopulationsphase. Die Paarbildung ist demnach ein individueller Prozeß, bei dem die Aktivitäten der im Revier als Werbung, die der als Revierwahl interpretiert werden.

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On pair-formation in the Sand Martin,Riparia riparia

Summary European Sand Martins arrive at their breeding sites in flocks of usually unmated and . Ringing results of a large population in NW-Germany and own observations indicate that the first flocks about a dozen individuals with an approximately balanced sex ratio appear at traditional breeding places and consist of older, experienced resident birds (presumably acquainted with one another). The birds arriving over the next several weeks are mainly first-year or non-resident individuals. The flocks arrive separately in areas with suitable sandcliffs, synchronize the pair-formation activities and avoid disturbances among paired and unpaired birds. This behaviour causes the formation of subcolonies, which are typical for all densely occupied breeding places. Each settles on a fixed area on the sandcliff (territory) in order to excavate a burrow, to sing the territory-song (fig. 2 b) and to perfor the territory-circle-flight (fig. 2 c, 4 a). Silent birds (normally ) are welcomed or tolerated by the resident . The sexes are monomorphic and therefore courtship displays of the are non-aggressive until establishment of pair-bonds. Only intruding singing or individually known neighbouring are driven away, usually at early stages of territory occupation. Unmated are normally shy and very sensitive to protracted disturbances. visit several occupied territories of the colony (fig. 1–3) in order to choose a burrow. leave territories which do not attract a . They settle new territories on the sandcliff, causing a surplus of burrows compared to breeding pairs in the colony. Activities which indicate the development of pair-bonds are: regular visits of a to a particular occupied territory with sporadic excavations by the ; aggressive activities of the towards other visitors usually , but sometimes at first even against the resident (i. e.: vocal threats, bill-gaping, pecking or pushing with the bill or vigorous face-to-face fights, fig. 3 b, 3 c). and sing the soft mating song at or in the burrow (fig. 1 c). Activities which indicate completed pair-bonds are: completion of the burrow by digging the nestchamber, predominantly done by the ; both birds staying together over long periods, both inside and outside the burrow; invitation-flight by the (fig. 4 b); and spending the night together in the burrow; beginning of nest-building, first only by the , then by both birds and finally only by the , accompanied by the (guarding-flight;, fig. 4c); mate-pursuit flights (sexual chases) during copulation phase, in which the singing pursues the silent , often accompanied by other (cp. fig. 4 d). Pair-formation in the Sand Martin occurs on individual territories and not, according toHickling (1959), within the flock.

     

Carotenoid pigments of Sorangium compositum (Myxobacterales) including two new carotenoid glucoside esters and two new carotenoid rhamnosides

Summary The carotenoid pigments of the myxobacterium Sorangium compositum were analyzed by chromatographical and chemical techniques and by visible, infra red, and mass spectroscopy. Besides -carotene, neurosporene, torulene, lycopene, and 1,2-dihydro-1-hydroxy--carotene, four new carotenoid glycosides were found. These pigments were identified as 1,2-dihydro-1-hydroxy-torulene glucoside ester (I), 1,2-dihydro-3,1-dihydroxy-torulene glucoside ester (III), 1,2-dihydro-1-hydroxy-torulene rhamnoside (II), and 1,2-dihydro-3,1-dihydroxytorulene rhamnoside (IV).Fifth communication on the carotenoids of myxobacteria. Fourth communication see Arch. Mikrobiol. 76, 364–380 (1971).     

Synthesis of disaccharide derivatives employing β-N-acetyl- d-hexosaminidase, β-d-galactosidase and β-d-glucuronidase

-N-Acetyl-d-hexosaminidase from Aspergillus oryzae catalysed the stereo- and regiospecific formation of the 6-O-benzylated disaccharide derivatives GalNAc1-3(6- OBn)Gal-SEt and GlcNAc1-3(6-OBn)Gal-SEt, which were obtained in transglycosylation reactions employing ethyl 6- O-benzyl-1-thio--d-galactopyranoside as acceptor. Preparative amounts of the chitobiose derivative GlcNAc1- 3GlcNAc-OPhNO2-p was prepared as well. - N-Acetyl-d-hexosaminidase from bovine testes catalysed the specific synthesis of GlcNAc1-3(6-OBn)GlcNH2-SEt and GalNAc1-3(6-OBn)GlcNH2-SEt, employing ethyl 2-amino-6-O-benzyl-2-deoxy-1-thio--d-glucopyranoside as acceptor. -d-Glucuronidase from E. coli was found to catalyse the formation of GlcA1-3(6-OBn)GlcNH2- SEt employing the same acceptor.     

Ultrastructure of the pituitary gland (pars distalis) in sockeye salmon (Oncorhynchus nerka) during gonad maturation

Summary The fine structure of the various hormone-producing cell types (with the exclusion of the prolactin cells) in the pituitary gland (pars distalis) of migratory sockeye salmon is described. All fish were in an advanced stage of sexual maturation. In the proximal pars distalis five cell types were distinguished: growth hormone cells, ACTH cells, gonadotrops, vesicular cells, and chromophobe cells. Gonadotrops were also found throughout the rostral pars distalis. A conspicuous feature of the gonadotrops was the presence of two kinds of secretory inclusions: small electron-dense granules (200–375 m) and large, relatively electron-translucent globules (400–2 000 m). The large vesicular cells, so called because of their conspicuous vesicular endoplasmic reticulum, were numerous and often appeared to contain some small granules. It is argued that they may represent a second type of gonadotropic cell, which, in earlier stages of gonad development, contains many granules but becomes largely degranulated near the time of reproduction when the other gonadotrops (globular gonadotrops) abound. The chromophobes, which were smaller and far less abundant than the vesicular cells, also appeared to contain small granules (120–280 m). They are probably thyrotrops.The assistance of Mr. S. Killick, of the International Pacific Salmon Fisheries Commission, who helped in the collection of salmon, is gratefully acknowledged.     

Feedback regulation of RNA polymerase subunit synthesis after the conditional overproduction of RNA polymerase in Escherichia coli

Summary The and subunit of RNA polymerase are thought to be controlled by a translational feedback mechanism regulated by the concentration of RNA polymerase holoenzyme. To study this regulation in vivo, an inducible RNA polymerase overproduction system was developed. This system utilizes plasmids from two incompatibility groups that carry RNA polymerase subunit genes under lac promoter/operator control. When the structural genes encoding the components of core RNA polymerase (, and ) or holoenzyme (, , and ⁷⁰) are present on the plasmids, induction of the lac promoter results in a two fold increase in the concentration of functional RNA polymerase. The induction of RNA polymerase overproduction is characterized by an initial large burst of synthesis followed by a gradual decrease as the concentration of RNA polymerase increases. Overproduction of RNA polymerase in a strain carrying an electrophoretic mobility mutation in the rpoB gene results in the specific repression of synthesis off the chromosome. These results indicate that RNA polymerase feedback regulation controls synthesis in vivo.     

DNA variations in regenerated plants of pea (Pisum sativum L.)

Summary The aim of this study was to determine whether DNA variations could be detected in regenerated pea plants. Two different genotypes were analyzed by cytogenetic and molecular techniques: the Dolce Provenza cultivar and the 5075 experimental line. Dolce Provenza regenerated plants showed a reduction in DNA content, particularly at the level of unique sequences and ribosomal genes. Moreover, regeneration was associated with an increase in DNA methylation of both internal and external cytosines of the CCG sequence. On the other hand, the DNA content of the 5075 line remained stable after regeneration. DNA reduction was found only in 5075 plants regenerated from callus cultures maintained for long incubation periods (about a year). The DNA variations observed are discussed both in relation to the genotype source and the role of tissue-culture stress.     

A light microscopic study of nuclear and cytoplasmic size of the aggregate acidophil population in the hypophysis cerebri,pars distalis,of adult male mule deer,Odocoileus hemionus hemionus,relative to seasons of the photoperiod and antler cycles

Summary Nuclear and cytoplasmic size (²) of acidophils in the pars distalis of adult male deer were measured and the data analyzed statistically with reference to the four classical seasons of the photoperiodic cycle and five periods and two events of the antler cycle. The seasons, and the respective mean cross-sectional areas of cell nuclei and cytoplasm, are: Spring (21 March–20 June; increasing photoperiod greater than 12 hours), 28.45 and 48.68 ²; Summer (21 June–20 September; decreasing photoperiod greater than 12 hours), 27.81 and 44.25 ²; Fall (21 September–20 December; decreasing photoperiod less than 12 hours), 30.40 and 45.07 ²; Winter (21 December–20 March; increasing photoperiod less than 12 hours) 27.28 and 40.30 ². Beginning in late winter and early spring the components of the antler cycle, and the respective cross-sectional areas of cell nuclei and cytoplasm, are: Initial Antler Growth, 28.08 and 38.58 ²; Growth of Velvet Antler Form, 28.93 and 50.61 ², Antlers Hardening, 27.53 and 40.83 ²; Velvet Shedding, 29.03 and 53.20 ²; Rutting Season, 29.95 and 44.97 ²; Preparation for Shedding, 26.50 and 40.38 ²; Antlers Recently Shed, 27.53 and 47.85 ². Shedding of boney antlers, growth of velvet antlers and increases in nuclear and cytoplasmic areas of acidophil cells in the pars distalis occur when the photoperiod is increasing. Construction and retention of hard antlers occur when photoperiod is decreasing. This lessening of day length appears to influence the gonadotrophs that regulate secretion of testosterone.A part of a dissertation submitted in partial fulfillment of the requirements for the degree Doctor of Philosophy, Anatomy, Colorado State University. Specimens were contributed by Colorado Federal Aid Project W-105-R, Colorado Division of Game, Fish and Parks, Game Research Center, Fort Collins and investigations of them was supported by grant T1-DE130 from the National Institutes of Health, Bethesda, Maryland, U.S.A.NIDR Predoctoral Trainee.     

Zur Frage des Zeipunktes einer Pr?gung auf die Heimatregion beim Halsbandschn?pper(Ficedula albicollis)

Zusammenfassung Junge Halsbandschnäpper wurden handaufgezogen, flogen im Flugkäfig aus und wurden dort selbständig. Darauf wurden sie 90 km nach Süden verfrachtet und in einem von dieser Art unbewohnten Gebiet freigelassen. Im nächsten Frühjahr siedelten sich mindestens 9 dort an, was 19% Rückkehrern entspricht, wenn die Hälfte der Vögel waren. kehrten in geringerer Zahl zurück und wurden nicht restlos erfaßt.Eine weitere Gruppe wurde erst vor Ende der Jugendmauser verfrachtet. Auch davon kehrten 18-19% der zurück. Ein Zeitraum von rund 2 Wochen vor dem Wegzug reichte also zur Prägung auf ein Gebiet als Heimat aus.Von einer dritten Gruppe von insgesamt 68 Schnäppern (= ca. 34 ), die erst nach Ende der Jugendmauser zur Wegzugzeit aufgelassen wurde, konnte später keiner nachgewiesen werden, auch nicht am Aufzuchtsort. Letzteres könnte an der Ungunst der örtlichen Verhältnisse liegen.Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

The stimulation of methylmercury production by decomposition of flooded birch leaves and jack pine needles

The link between methylmercury (MeHg) production and decomposition of flooded organic matter was examined using an enclosure experiment. Six plastic enclosures were filled with lake water containing low concentrations of dissolved organic carbon (146µmolL^–1) and MeHg (0.02ngL^–1) and anchored in a lake at the Experimental Lakes Area, northwestern Ontario. Either fresh birch leaves, fresh jack pine needles, or no plant tissues at all were added to enclosures. Birch leaves decomposed 2.4 times faster than jack pine needles as measured by the total carbon decomposition by-products produced in enclosures over time. However, measured net MeHg production in enclosures containing birch leaves (0.35±0.05ng per g carbon added) was five times lower than in the enclosures containing jack pine needles (1.94±0.28ng per g carbon added). These results showed that MeHg production is not solely related to rates of organic matter decomposition, and that increases in MeHg associated with flooded birch leaves and jack pine needles resulted from the production of new MeHg as opposed to leaching of MeHg already in the plant tissues during decomposition.     

Interactions of protein kinase CK2β subunit within the holoenzyme and with other proteins

Protein kinase CK2 is a ubiquitous, highly conserved protein kinase with a tetrameric 22 structure. For the formation of this tetrameric complex a - dimer seems to be a prerequisite. Using the two-hybrid system and a series of CK2 deletion mutants, we mapped domains involved in - and - interactions. We also detected an intramolecular b interaction within the amino acid stretch 132-165.Using CK2 as a bait in a two-hybrid library screening several new putative cellular partners have been identified, among them the S6 kinase p90rsk, the putative tumor suppressor protein Doc-1, the Fas-associated protein FAF1, the mitochondrial translational initiation factor 2 and propionyl CoA carboxylase subunit.     

13Cα and 13Cβ chemical shifts as a tool to delineate β-hairpin structures in peptides

Unravelling the factors that contribute to the formation and the stability of -sheet structure in peptides is a subject of great current interest. A -hairpin, the smallest -sheet motif, consists of two antiparallel hydrogen-bonded -strands linked by a loop region. We have performed a statistical analysis on protein -hairpins showing that the most abundant types of -hairpins, 2:2, 3:5 and 4:4, have characteristic patterns of ¹³C and ¹³C conformational shifts, as expected on the basis of their and angles. This fact strongly supports the potential value of ¹³C and ¹³C conformational shifts as a means to identify -hairpin motifs in peptides. Their usefulness was confirmed by analysing the patterns of ¹³C and ¹³C conformational shifts in 13 short peptides, 10–15 residues long, that adopt -hairpin structures in aqueous solution. Furthermore, we have investigated their potential as a method to quantify -hairpin populations in peptides.     

The cytology of phytophthora infestans

Summary Phytophthora infestans has three kinds of somatic nuclei: an oval shaped nucleus (approx. 3.1×2.7 ) which stains diffusely except for a crescent shaped Feulgen positive cap which stains intensely; a granular nucleus whose contents are organized into a fairly constant number of stained bodies, and, a deeply staining condensed nucleus. The capped nucleus is thought to be metabolic or resting and the granular nucleus is thought to be dividing as it is most commonly found in hyphal tips. Attenuated forms of all three kinds of nuclei are found.Nuclear division is mitotic and intranuclear. Eight—ten chromosomes are seen at metaphase.Sporangia have a mean of 6.3 nuclei which is constant for age and strain of culture. Sporangia become multinucleate as a result of nuclear migration and not by division in the developing sporangium. Zoospores are usually uninucleate.The nuclear cap is persistent throughout nuclear division when it also divides. It is associated with flagella production and nuclear migration and has some of the properties of a blepharoplast.     

Isoform-Specific Membrane Translocation of Protein Kinase C After Ischemic Preconditioning

Mild cerebral anoxic/ischemic/stress insults promote tolerance and thereby protect the brain from subsequent lethal anoxic/ischemic insults. We examined whether specific activation of PKC , , , or isoforms is associated with ischemic preconditioning (IPC) in rat brain. IPC was produced by a 2-minute global cerebral ischemia. Membrane and cytosolic fractions of the hippocampi were immunoblotted using specific antibodies for PKC, , , and . PKC showed a significant translocation to the membrane fraction from 30 min to 4 h and PKC at 4 h following IPC. In contrast, the membrane/cytosol ratio of PKC showed a tendency to decrease at 30 min and 8 h, and the membrane/cytosol ratio of PKC was significantly decreased from 30 min to 24 h following IPC. These findings indicate PKC isoform-specific membrane translocations in the hippocampus after brief global brain ischemia and suggest that activation of PKC and PKC may be associated with IPC-induced tolerance in the rat hippocampus.     

Diversity of the mouse T cell receptor Cγ1 gene: structural analysis in C57BL/Ka

We have isolated an unusual T cell receptor chain cDNA clone (7.1) from a library made from RNA derived from adult thymus of C57BL/Ka mice. This cDNA clone corresponds to the appropriately processed C1 constant region exons preceded by 1.5 kb of J-C1 intron. The 7.1 coding region is extremely homologous to the C1 gene of BALB/c mice, differing at the protein level by a single deletion (alanine 139) and a single substitution. This latter change eliminates the sole N-linked sugar attachment site, providing a basis for strain-specific glycosylation patterns. The J-C1 intronic region contains two DNA segments (termed J1 and J2) that are highly reminiscent of joining (J) segments; both have potentially functional recombination and donor splice sequences flanking an open reading frame. Northern analysis suggests that 7.1 may be derived from a large, variable region-containing precursor.     

The “Bantu Clinic”: A Genealogy of the African Patient as Object and Effect of South African Clinical Medicine, 1930–1990

This paper is about power, medicine andthe identity of the African as a patient of westernmedicine. From a conventional perspective and asencoded in the current quest for wholeness thatcharacterises South African biomedical discourse, theAfrican patient – like any other patient – has alwaysexisted as an authentic and subjectified being, whosetrue attributes and experiences have been denied bythe mechanistic, reductionistic and ethnocentricpractices of clinical medicine. Against this liberalhumanist perspective on the body as ontologicallyindependent of power, this paper offers a Foucaultianreading of the African patient as – like any otherpatient – contingent upon the force relations immanentwithin and relayed through the clinical practices ofbiomedicine. A quintessential form of disciplinarymicro-power, these fabricate the most intimaterecesses of the human body as manageable objects ofmedical knowledge and social consciousness to makepossible the great control strategies of repression,segmentation and liberation that are the usual focusof conventional investigations into the place andfunction of medicine in society. Since the 1930s whenthe African body first emerged as a discrete object ofa secular clinical knowledge, these have repeatedlytransformed the attributes and identity of the Africanpatient, and the paper traces this archaeology ofSouth African clinical perception from then until the1990s to show how its quest for wholeness is not anend point of discovery or liberation, but merelyanother ephemeral crystallization of socio-medicalknowledge in a constantly changing force field ofdisciplinary power.     

Ultrastructure of four types of striated muscle fibers in the atlantic hagfish (Myxine glutinosa,L.)

Summary Four types of striated muscle fibers with distinctive ultrastructure were defined in the Atlantic hagfish (Myxine glutinosa, L.): white, intermediate, and red fibers of m. parietalis, and red fibers of m. craniovelaris.White fibers are thick, contain very few mitochondria and fat vacuoles, and possess distinct and separate myofibrils with thin Z-disks and distinct M-lines. Intermediate fibers are thinner, possess largely similar myofibrils that often are even better separated due to a higher content of fat vacuoles and especially mitochondria and glycogen granules. Red fibers of m. parietalis contain large amounts of mitochondria, fat vacuoles, and glycogen granules. Their myofibrils possess M-lines, and although branching more, the myofibrils of red fibers conform with a Fibrillenstruktur pattern like those of white and intermediate fibers. Red fibers of m. craniovelaris are very thin, possess many smaller fat vacuoles, and large amounts of mitochondria and glycogen granules. The myofibrils are significantly thinner than in m. parietalis fibers, run as quite independent well separated units, possess thicker Z-disks, and lack M-lines. Large amounts of myosatellite cells are associated with these red fibers.Triads are located near A/I-junctions in all four fiber types and occur irregularly, the density of triads being different in the various fiber types.We are indebted to Dr. Finn Walvig, Biological Station, University of Oslo, Drøbak, for supply of hagfishes, and we also wish to thank Dr. Jan K. S. Jansen, Institute of Physiology, University of Oslo, for valuable suggestions during this study.     

Enzyme-catalyzed synthesis of alkyl β-D-glycosides with crude homogenate ofSulfolobus solfataricus

Summary Crude homogenate of thermophilic archaebacteriumSulfolobus solfataricus, possessing a -glycosidase, has been used to synthesize different alkyl -D-glycosides starting from phenyl -D-glucoside, phenyl -D-galactoside and lactose as carbohydrate donors. High product yield (95% with respect to the carbohydrate donor) of octyl -D-glucoside has been obtained in a two-phase system containing 5% of water. The enantioselection for the galactosyl transfer to the secondary hydroxyl group of propane-1,2-diol is higher than that found using -galactosidase fromE. coli.     

The chromosomal localization of human β-galactosidase revisited: a locus for β-galactosidase on human chromosome 3 and for its protective protein on human chromosome 22

Summary A series of man-Chinese hamster and man-mouse somatic cell hybrids was investigated to study the localization of the genes coding for the human lysosomal enzyme -galactosidase (EC 3.2.1.23) and for its protective protein. Using a monoclonal antibody, raised against human placental -galactosidase, it was observed that the structural locus for the -galactosidase polypeptide is located on chromosome 3. The nature of the involvement of chromosome 22 in the expression of human -galactosidase was elucidated by metabolic labelling of the hybrids with radioactive amino acids, immunoprecipitation with monoclonal and polyclonal antibodies against -galactosidase, followed by analysis via gel electrophoresis and fluorography.The data show that the presence of chromosome 22 coincides with the presence of a 32 kd protein. This polypeptide, the protective protein was previously shown to be intimately associated with human -galactosidase. In addition, the protective protein was found to be essential for the in vivo stability of -galactosidase by aggregating -galactosidase monomers into high molecular weight multimes. Both chromosome 3 and 22 are therefore necessary to obtain normal levels og -galactosidase activity in human cells.     

Evolutionary origin of the class A and class C β-lactamases

Summary The protein sequences of 18 class A -lactamases and 2 class C -lactamases were analyzed to produce a rooted phylogenetic tree using the DD peptidase of Streptomyces R61 as an outgroup. This tree supports the penicillin-binding proteins as the most likely candidate for the ancestoral origin of the class A and class C -lactamases, these proteins diverging from a common evolutionary origin close to the DD peptidase. The actinomycetes are clearly shown as the origin of the class A -lactamases found in other non-actinomycete species. The tree also divides the -lactamases from the Streptomyces into two subgroups. One subgroup is closer to the DD peptidase root. The other Streptomyces subgroup shares a common branch point with the rest of the class A -lactamases, showing this subgroup as the origin of the non-actinomycete class A -lactamases. The non-actinomycete class A -lactamase phylogenetic tree suggests a spread of these -lactamases by horizontal transfer from the Streptomyces into the non-actinomycete gram-positive bacteria and thence into the gram-negative bacteria. The phylogenetic tree of the Streptomyces class A -lactamases supports the possibility that horizontal transfer of class A -lactamases occurred within the Streptomyces.