The key difference between signal sequence and signal patch is that signal sequence is an amino acid sequence in proteins that helps to prompt a cell to translocate proteins to organelles or cellular membrane, while the signal patch is an amino acid sequence in proteins that helps to prompt a cell to translocate proteins from cytosol to nucleus.
Protein targeting or sorting is the biological mechanism by which proteins are transported to their appropriate locations within or outside the cell. The information that is contained in the protein itself directs this delivery process. Correct protein sorting is crucial for the cell. The errors or dysfunction in sorting can cause multiple diseases. Signal sequence and signal patch are two sequences made up of amino acids in proteins that participate in protein targeting or sorting.
CONTENTS
1. Overview and Key Difference
2. What is a Signal Sequence
3. What is a Signal Patch
4. Similarities – Signal Sequence and Signal Patch
5. Signal Sequence vs Signal Patch in Tabular Form
6. Summary – Signal Sequence vs Signal Patch
What is a Signal Sequence?
The signal sequence is an amino acid sequence in the proteins that prompts the cell to translocate the proteins, usually to organelles or the cellular membrane. A signal sequence is also known as a signal peptide. It is a short peptide that contains 16 to 30 amino acids. It is present at the N terminus (occasionally C terminus) of most newly synthesized proteins. Signal sequence assists proteins toward secretory pathways. The proteins that contain signal sequences include those that reside inside organelles (endoplasmic reticulum, Golgi apparatus, or endosomes), secreted from the cell or inserted into most cellular membranes.
Normally, most type I membrane-bound proteins have signal sequences. However, the majority of type II and multispanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain known as the “target peptide.” Moreover, in prokaryotes, the signal sequences direct the newly synthesized proteins to the SecYEG protein conducting channel that is present in the plasma membrane. Furthermore, in eukaryotes, a homologous system exists, where the signal sequences direct the newly synthesized proteins to the Sec61 channel. Though this channel shares structural and sequence homology with SecYEG, it is present in the endoplasmic reticulum.
What is a Signal Patch?
A signal patch is an amino acid sequence in the proteins that prompts a cell to translocate proteins from the cytosol to the nucleus. A signal patch contains information to send a given protein to the indicated location in the cell. Most probably, the signal path directs protein from cytosol to the nucleus. It is made up of amino acid residues that are distant from one another in the primary sequence. However, these amino acids are located close to each other in the tertiary structure of the folded protein.
Unlike signal sequences, signal patches are not cleaved from the mature protein after the sorting process. Signal patches are very hard to predict. Nuclear localization signals are generally signal patches, although some signal sequences also exist. Moreover, signal patches are found on proteins destined for the nucleus, which enable their selective transport from the cytosol into the nucleus through nuclear pore complexes.
What are the Similarities Between Signal Sequence and Signal Patch?
- Signal sequence and signal patch are two sequences involved in protein targeting or sorting.
- Both sequences are present inside proteins.
- These sequences are short amino acid sequences.
- The errors in both sequences can cause dysfunction in protein sorting, which results in multiple diseases.
What is the Difference Between Signal Sequence and Signal Patch?
The signal sequence is an amino acid sequence found in the proteins that prompts a cell to translocate the proteins to the organelles or the cellular membrane, while the signal patch is an amino acid sequence found in the proteins that prompts a cell to translocate proteins usually from the cytosol to nucleus. Thus, this is the key difference between signal sequence and signal patch. Furthermore, the signal sequence is cleaved by mature proteins after sorting, while the signal patch is not cleaved by mature proteins after sorting.
The following table summarizes the difference between signal sequence and signal patch.
Summary – Signal Sequence vs Signal Patch
Signal sequence and signal patch are two sequences found within proteins. They are necessary for protein targeting or sorting. Signal sequence prompts a cell to translocate the proteins, usually to organelles or the cellular membrane. On the other hand, a signal patch prompts a cell to translocate proteins, usually from the cytosol to the nucleus. So, this is the key difference between signal sequence and signal patch.
Reference:
1. “Signal Peptide.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Signal sequence” By Yikrazuul – Own work; PMID 9789330 (CC BY-SA 3.0) via Commons Wikimedia
2. “Bipartite NLS sites C22orf15” By Rade0120 – Own work (CC BY-SA 4.0) via Commons Wikimedia
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