Symporters: Membrane transporters that co-transport two or more dissimilar molecules in the same direction across a membrane. Usually the transport of one ion or molecule is against its electrochemical gradient and is "powered" by the movement of another ion or molecule with its electrochemical gradient.Plasma Membrane Neurotransmitter Transport Proteins: A family of neurotransmitter transporter proteins that facilitate NEUROTRANSMITTER reuptake into PRESYNAPTIC TERMINALS. They may play a role in regulating the intensity and duration of neurotransmission.Chlorella: Nonmotile unicellular green algae potentially valuable as a source of high-grade protein and B-complex vitamins.Proton-Phosphate Symporters: Proteins that cotransport hydrogen ions and phosphate ions across cellular membranes.Sodium-Phosphate Cotransporter Proteins: A family of symporters that facilitate sodium-dependent membrane transport of phosphate.Sodium-Glucose Transporter 1: The founding member of the sodium glucose transport proteins. It is predominately expressed in the INTESTINAL MUCOSA of the SMALL INTESTINE.Amino Acid Transport Systems: Cellular proteins and protein complexes that transport amino acids across biological membranes.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.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.Carrier Proteins: Transport proteins that carry specific substances in the blood or across cell membranes.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.Monosaccharide Transport Proteins: A large group of membrane transport proteins that shuttle MONOSACCHARIDES across CELL MEMBRANES.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Leucine: An essential branched-chain amino acid important for hemoglobin formation.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Protein Structure, Secondary: The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to alpha helices, beta strands (which align to form beta sheets) or other types of coils. This is the first folding level of protein conformation.Sodium Chloride Symporters: A subclass of symporters found in KIDNEY TUBULES, DISTAL that are the major pathway for salt resorption. Inhibition of these symporters by BENZOTHIADIAZINES is the basis of action of some DIURETICS.Xenopus laevis: The commonest and widest ranging species of the clawed "frog" (Xenopus) in Africa. This species is used extensively in research. There is now a significant population in California derived from escaped laboratory animals.Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Oocytes: Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).Bacterial Proteins: Proteins found in any species of bacterium.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.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).Sodium-Bicarbonate Symporters: Proteins that cotransport sodium ions and bicarbonate ions across cellular membranes.Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.Kinetics: The rate dynamics in chemical or physical systems.Sodium-Potassium-Chloride Symporters: A subclass of symporters that specifically transport SODIUM CHLORIDE and/or POTASSIUM CHLORIDE across cellular membranes in a tightly coupled process.