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Related Concept Videos

The Significance of Membrane Transport01:44

The Significance of Membrane Transport

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The transport of solutes across the cell membrane is essential for metabolic processes, like maintaining cell size and volume, generating the action potential, exchanging nutrients and gases, etc. Membrane transport can be either passive or active. It can be simple diffusion, facilitated, or mediated transport aided by transport proteins such as transporters and channels.
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...
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Protein Transport to the Thylakoids01:22

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Thylakoids are membrane-bound sac-like structures within the chloroplast that serve as sites for photosynthesis. Thylakoid lumen contains many electron transport proteins and is enclosed by a thylakoid membrane rich in the light-harvesting complex. Proteins targeted to the thylakoids are transported as precursors and are sorted by the general TOC/TIC import pathway. Once the precursor reaches the stroma, stromal processing peptidases remove their transit signal and expose thylakoid signal...
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Cotranslational Protein Translocation01:20

Cotranslational Protein Translocation

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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
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Overview of Protein Sorting and Transport01:45

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Eukaryotic cells have different membrane-bound organelles with distinct protein requirements. The process by which proteins are targeted to a specific organelle is called protein sorting.
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation.  In gated transport, folded...
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Protein Transport to the Outer Chloroplast Membrane01:11

Protein Transport to the Outer Chloroplast Membrane

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Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
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Primary Active Transport01:29

Primary Active Transport

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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...
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A Bioinformatics Pipeline for Investigating Molecular Evolution and Gene Expression using RNA-seq
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Tracing pathways of transport protein evolution.

Milton H Saier1

  • 1Division of Biological Sciences, University of California at San Diego, La Jolla 92093-0116, USA. msaier@ucsd.edu

Molecular Microbiology
|June 6, 2003
PubMed
Summary

Bioinformatic analyses reveal integral membrane transport proteins evolved independently. Gene duplication and other events shaped transporter diversity and topology over evolutionary time.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Bioinformatics

Background:

  • Integral membrane transport proteins are crucial for cellular function.
  • These proteins often exhibit complex structures with multiple transmembrane segments.
  • Understanding their evolutionary origins is key to comprehending their diversity.

Purpose of the Study:

  • To investigate the evolutionary origins of integral membrane transport proteins.
  • To identify the mechanisms driving the diversification of transporter families.
  • To elucidate the pathways involved in the emergence of transporter proteins.

Main Methods:

  • Bioinformatic analysis of integral membrane transport proteins across numerous families.
  • Examination of gene duplication, fusion, splicing, deletion, and insertion events.

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Analysis of Endocytic Uptake and Retrograde Transport to the Trans-Golgi Network Using Functionalized Nanobodies in Cultured Cells
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Analysis of Endocytic Uptake and Retrograde Transport to the Trans-Golgi Network Using Functionalized Nanobodies in Cultured Cells

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Analysis of Endocytic Uptake and Retrograde Transport to the Trans-Golgi Network Using Functionalized Nanobodies in Cultured Cells
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  • Analysis of amino acid substitutions and their impact on protein topology.

    • Main Results:

    • Transporter families primarily function in transport, with rare exceptions.
    • Intragenic duplication events (duplication, triplication, quadruplication) significantly increased transmembrane alpha-helical hydrophobic segments (TMSs).
    • Gene fusion, splicing, deletion, insertion, and amino acid substitutions contributed to topological diversity and altered protein structures.

    Conclusions:

    • Many transporter families originated independently.
    • Evolutionary mechanisms like gene duplication and amino acid substitutions played critical roles in shaping transporter structure and function.
    • Specific evolutionary pathways for the appearance of transporter families can be postulated.