Topology of allosteric regulation of lactose permease

Sugar transport by some permeases in Escherichia coli is allosterically regulated by the phosphorylation state of the intracellular regulatory protein, enzyme IIAglc of the phosphoenolpyruvate:sugar phosphotransferase system. A sensitive radiochemical assay for the interaction of enzyme IIAglc with membrane-associated lactose permease was used to characterize the binding reaction. The binding is stimulated by transportable substrates such as lactose, melibiose, and raffinose, but not by sugars that are not transported (maltose and sucrose). Treatment of lactose permease with N-ethylmaleimide, which blocks ligand binding and transport by alkylating Cys-148, also blocks enzyme IIAglc binding. Preincubation with the substrate analog β-d-galactopyranosyl 1-thio-β-d-galactopyranoside protects both lactose transport and enzyme IIAglc binding against inhibition by N-ethylmaleimide. A collection of lactose permease replacement mutants at Cys-148 showed, with the exception of C148V, a good correlation of relative transport activity and enzyme IIAglc binding. The nature of the interaction of enzyme IIAglc with the cytoplasmic face of lactose permease was explored. The N- and C-termini, as well as five hydrophilic loops in the permease, are exposed on the cytoplasmic surface of the membrane and it has been proposed that the central cytoplasmic loop of lactose permease is the major determinant for interaction with enzyme IIAglc. Lactose permease mutants with polyhistidine insertions in cytoplasmic loops IV/V and VI/VII and periplasmic loop VII/VIII retain transport activity and therefore substrate binding, but do not bind enzyme IIAglc, indicating that these regions of lactose permease may be involved in recognition of enzyme IIAglc. Taken together, these results suggest that interaction of lactose permease with substrate promotes a conformational change that brings several cytoplasmic loops into an arrangement optimal for interaction with the regulatory protein, enzyme IIAglc. A topological map of the proposed interaction is presented.

Applicazione dell’Indice di Funzionalità Fluviale (I.F.F.) al fiume Segura nella provincia di Alicante

L’obiettivo di questo studio è la valultazione della funzionalità ecologica del fiume Segura nella provincia di Alicante (Spagna) mediante l’applicazione dell’IFF (Indice di Funzionalità Fluviale). La motivazione di questa scelta è stata la volontà di partecipare all’introduzione di questo indice in Spagna, paese in cui non è abitualmente utilizzato. Sono stati valutati 24006 m di corso d’acqua suddivisi in 24 tratti di varie lunghezze, partendo dall’uscita del centro urbano di Orihuela fi no al centro abitato di Guardamar del Segura. Il giudizio della funzionalità del fiume complessivamente rientra nell’intervallo dei livelli da V a III-IV, con una percentuale maggiore dell’80% di livello IV sia per la sponda destra che per la sinistra. L’applicazione dell’Indice ha permesso non solo di valutare la funzionalità dei 24 tratti, ma anche di individuare i parametri più degradati del corso d’acqua e i parametri più «forti», dall’osservazione dei quali è possibile far partire un lavoro di ripristino ambientale e rinaturalizzazione del fiume.

La villa de la C/ Olimpo y la organización territorial de la periferia urbana de Lucentum (Alicante)

Esta investigación establece la secuencia estratigráfica, cronológica y funcional de un núcleo de poblamiento suburbano del municipio romano de Lucentum, con el fin de dibujar las líneas maestras de la evolución productiva de su ager periurbano. El yacimiento presenta cuatro fases principales que abarcan un dilatado arco temporal: estructuras de época tardorrepublicana (fase I, ss. II-I aC), una reestructuración viaria y urbanística de época augustea (fase II), el desarrollo de una villa con estructuras de transformación mercantil datada a partir de época tardojulia o flavia (fase III) y, por último, una fase bajoimperial (fase IV, ss. IV-v dC), en la que la villa sufre fuertes reestructuraciones.

The poetical works of Edmund Spenser.

Illustrated title pages.

Terry clock chronology /

"Sources": p. iv-v.

Health and physical education series of the state of Ohio, Department of education ... prepared with the approval of B.O. Skinner, director of education.

Includes bibliographies.

The country dance book ...

Vols. IV-V have imprint: London, Novello and company, limited New York, The H. W. Gray co.

Effective speech, including public speaking, mental training and the development of personality /

v. 1. Manual I-II. -- v. 2. Manual III-IV. -- v. 3. Manual V-VI. -- v. 4. Manual VII-VIII. -- v. 5. Manual IX-X. -- v. 6. Manual XI-XII.

La préparation évangélique.

[1] Introduction génŕale. Livre I.--[2] Livres II-III.--[3] Livres IV-V, 1-17.--[4] Livres V, 18-26-VI.--[5] Livre VII.--[6] Livres VIII-IX-X.--[7] Livre XI.--[8] Livres XII-XIII.--[9] Livres XIV-XV.

Calendar of inquisitions post mortem and other analogous documents preserved in the Public Record Office /

Includes indexes.

P. Vergili Maronis Aeneidos libri I [- ] ...

Includes bibliographical references.

The history of modern Europe. With an account of the decline and fall of the Roman empire: and a view of the progress of society, from the rise of the modern kingdoms to the peace of Paris, in 1763.

Vols. 2 and 4 printed by Robert Carr; v. 3 by John Bioren.

The lives of the Lord Chancellors and Keepers of the Great Seal of England.

Vol. 8, edited after the author's death, by Mary Scarlett Campbell, 1869.

A history of our own times ...

I-II. From the accession of Queen Victoria to the general election of 1880.--III. From 1880 to the diamond jubilee.--IV-V. From the diamond jubilee, 1897, to the accession of King Edward VII.

Discours parlementaires de M. Thiers;

t. I-III. 1830-1836.--t. IV-V. 1837-1841.--t. VI. 1842-1845.--t. VII. 1846-1848.--t. VIII. 1848-1850.--t. IX. 1850-1864.--t. X. 1865-1866.--t. XI. 1867-1868.--t. XII. 1868-1870.--t. XIII. 1871.--t. XIV. 1872.--t. XV. 1872-1877.-t. XVI. Table générale, analytique et alphabétique ...