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Related Concept Videos

Electron Transport Chain Components01:29

Electron Transport Chain Components

The electron transport chain (ETC) is a crucial metabolic pathway that facilitates energy conversion in prokaryotic and eukaryotic cells. In eukaryotes, the ETC comprises four membrane-associated protein complexes in the inner mitochondrial membrane. In prokaryotes, the ETC in the plasma membrane can vary in composition, with fewer or different complexes depending on the organism and environmental conditions. These complexes transfer electrons from electron donors, such as NADH and FADH2, to...
ATP Driven Pumps II: P-type Pumps01:34

ATP Driven Pumps II: P-type Pumps

The P-type pumps are a large family of integral membrane transporter ATPases. They are divided into five major types based on substrate specificity, from I to V.
A typical P-type pump has three cytosolic domains: nucleotide-binding (N), phosphorylation (P), and activator (A) domains. These domains are connected to the membrane-spanning helices by short amino acid segments. ATP hydrolysis and covalent phosphoenzyme intermediate formation are crucial parts of the catalytic cycle. At the highly...
Anoxygenic Photosynthesis01:30

Anoxygenic Photosynthesis

Anoxygenic photosynthesis is a phototrophic process that captures light energy to drive carbon fixation without producing molecular oxygen. Unlike oxygenic photosynthesis, which utilizes water as an electron donor and releases oxygen, anoxygenic phototrophs use alternative electron donors such as hydrogen sulfide (H₂S), elemental sulfur (S⁰), or thiosulfate (S₂O₃²⁻). This process is carried out by diverse groups of bacteria, including purple bacteria, green sulfur bacteria, heliobacteria, and...
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Other Unique Bacteria

Magnetic bacteria exhibit a directed movement called magnetotaxis, driven by structures called magnetosomes. These magnetosomes consist of chains of magnetic particles made of either magnetite (Fe₃O₄) or greigite (Fe₃S₄) and are organized in a linear conformation by a protein scaffold within invaginations of the cell membrane. The bacteria align along the north–south magnetic field lines, much like a compass needle. They are typically microaerophilic or anaerobic and are commonly found near the...
ATP Driven Pumps I: An Overview01:27

ATP Driven Pumps I: An Overview

ATP-driven pumps, also known as transport ATPases, are integral membrane proteins. They have binding sites for ATP located on the membrane's cytosolic side and the ion-conducting domain in the transmembrane region. These pumps use the free energy released from ATP hydrolysis to move the solutes across cell membranes against an electrochemical gradient.
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Primary Active Transport

In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or electrochemical gradient. There are two types of active transport: primary active transport and secondary active transport. Primary active transport utilizes chemical energy from ATP to drive protein pumps embedded in the cell membrane. With energy from ATP, the pumps transport ions against their electrochemical gradients—a direction they would not...

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In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa
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A light-driven sodium ion pump in marine bacteria.

Keiichi Inoue1, Hikaru Ono, Rei Abe-Yoshizumi

  • 1Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.

Nature Communications
|April 12, 2013
PubMed
Summary

Researchers discovered a new light-driven sodium ion pump in marine bacteria. This microbial rhodopsin, KR2, pumps sodium ions and can also pump protons, suggesting a significant role in cellular energy.

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Area of Science:

  • Microbiology
  • Biochemistry
  • Photobiology

Background:

  • Microbial rhodopsins are light-driven proteins that generate cellular energy.
  • Proton-pumping rhodopsins are well-established, converting light energy into proton gradients.
  • The functional diversity of microbial rhodopsins is still being explored.

Purpose of the Study:

  • To identify and characterize novel microbial rhodopsins with unique ion-pumping capabilities.
  • To investigate the ion selectivity and function of rhodopsins from the marine flavobacterium Krokinobacter eikastus.
  • To explore the potential significance of light-driven ion pumps in microbial ecosystems.

Main Methods:

  • Genomic analysis to identify rhodopsin genes in Krokinobacter eikastus.
  • Heterologous expression and functional characterization of identified rhodopsins.
  • Spectroscopic analysis to determine ion binding and transport mechanisms.

Main Results:

  • Krokinobacter eikastus possesses two rhodopsins: KR1 (proton pump) and KR2 (sodium ion pump).
  • Rhodopsin KR2 exhibits outward sodium ion pumping and can also pump lithium ions.
  • KR2 functions as a proton pump in the presence of potassium chloride or larger cations, indicating it is a compatible sodium ion-proton pump.
  • Spectroscopic data confirm sodium ion binding in the extracellular domain of KR2.

Conclusions:

  • Discovery of a novel functional class: light-driven sodium ion pumps.
  • Rhodopsin KR2 represents a versatile ion transporter with implications for cellular bioenergetics.
  • Light-driven sodium pumps may play a crucial role in microbial environments, comparable to proton pumps.