Biomaterial Database

Helix packing in the lactose permease of Escherichia coli: localization of helix VI. 2001

L Guan, and A B Weinglass, and H R Kaback

Howard Hughes Medical Institute, University of California Los Angeles, Los Angeles, CA 90095-1662, USA.

Plasmids encoding "split" lactose permease constructs with discontinuities in either the periplasmic loop between helices V and VI (N(5)/C(7)) or between helices VI and VII (N(6)/C(6)) were used to localize helix VI within the tertiary structure by site-directed thiol cross-linking. A total of 57 double-Cys pairs, with one Cys residue in helix VI and another in helix V or VIII, were studied with homobifunctional cross-linking agents. Significant cross-linking is observed between the periplasmic ends of helices V (position 158 or 161) and VI (position 170) with rigid 6 or 10 A reagents. Furthermore, the Cys residue at position 170 (helix VI) also cross-links to a Cys residue at either position 264 or 265 (helix VIII) with a 21 A cross-linking agent. The data indicate that helices V, VI and VIII are in close proximity at the periplasmic face of the membrane, with helix VI significantly closer to helix V. In addition, beta,D-galactopyranosyl 1-thio-beta,D-galactopyranoside induces a significant increase in cross-linking efficiency between helices VI and VIII and between helices V and VIII, with no significant change in cross-linking between helices V and VI.

UI	MeSH Term	Description	Entries
D008024	Ligands	A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)	Ligand
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D009004	Monosaccharide Transport Proteins	A large group of membrane transport proteins that shuttle MONOSACCHARIDES across CELL MEMBRANES.	Hexose Transport Proteins,Band 4.5 Preactin,Erythrocyte Band 4.5 Protein,Glucose Transport-Inducing Protein,Hexose Transporter,4.5 Preactin, Band,Glucose Transport Inducing Protein,Preactin, Band 4.5,Proteins, Monosaccharide Transport,Transport Proteins, Hexose,Transport Proteins, Monosaccharide,Transport-Inducing Protein, Glucose
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D003432	Cross-Linking Reagents	Reagents with two reactive groups, usually at opposite ends of the molecule, that are capable of reacting with and thereby forming bridges between side chains of amino acids in proteins; the locations of naturally reactive areas within proteins can thereby be identified; may also be used for other macromolecules, like glycoproteins, nucleic acids, or other.	Bifunctional Reagent,Bifunctional Reagents,Cross Linking Reagent,Crosslinking Reagent,Cross Linking Reagents,Crosslinking Reagents,Linking Reagent, Cross,Linking Reagents, Cross,Reagent, Bifunctional,Reagent, Cross Linking,Reagent, Crosslinking,Reagents, Bifunctional,Reagents, Cross Linking,Reagents, Cross-Linking,Reagents, Crosslinking
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D001692	Biological Transport	The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.	Transport, Biological,Biologic Transport,Transport, Biologic
D013862	Thiogalactosides	Galactosides in which the oxygen atom linking the sugar and aglycone is replaced by a sulfur atom.	Thiogalactopyranosides
D026901	Membrane Transport Proteins	Membrane proteins whose primary function is to facilitate the transport of molecules across a biological membrane. Included in this broad category are proteins involved in active transport (BIOLOGICAL TRANSPORT, ACTIVE), facilitated transport and ION CHANNELS.	Biological Pump,Membrane Transport Protein,Membrane Transporter,Membrane Transporters,Metabolic Pump,Permease,Biological Pumps,Metabolic Pumps,Permeases,Pump, Biologic,Pump, Biological,Pump, Metabolic,Pumps, Biological,Pumps, Metabolic,Biologic Pump,Protein, Membrane Transport,Transport Protein, Membrane,Transport Proteins, Membrane,Transporter, Membrane,Transporters, Membrane