Questions tagged [protein-structure]

The 3-dimensional organisation of amino acids in a protein, specifically including the secondary, tertiary and quaternary structures.

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67 views

What is meant by “unique ligand” on the RCSB Protein Data Bank website?

I went to the https://www.rcsb.org/ site, and searched for some proteins. For each entry, “unique ligands” are listed. I understand a ligand is a molecule or ion that binds to a metal atom. I don’t ...
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Maximum subarray problem for genomic sequence analysis

Genomic sequence analysis employs maximum subarray algorithms to identify important biological segments of protein sequences. These problems include conserved segments, GC-rich regions, tandem repeats,...
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Are all organelle lumens a reducing environment like the cytosol, or nonreducing like the extracellular space and the ER lumen?

I am interested to know if cysteine can form disulphide bridges in proteins within organelles. Typically cysteine will not form disulphide bonds in the reducing environment of the cytosol, but will in ...
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36 views

What is the point of calculating extinction coefficients of a protein without Cys residues?

ProtParam computes various physico-chemical properties that can be deduced from a protein sequence. One of these parameters are "Extinction coefficients". They provide two values. One value ...
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Differentiating molecules based on peptide sequence? How to annotate?

I want to differentiate between classical class I and non classical class I MHC molecules in a model organism using well conserved structural features within classical MHC I molecules (eg intradomain ...
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48 views

SARS-CoV - relative size of the spike protein

I was given the task of determining the percentage of the S-protein of the SARS-CoV relative to the total of its proteins from the attached image. However, I have been given no explanation of the ...
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1answer
56 views

What's superposition and thread in RosettaCM?

I'm a beginner in structural biology. I had a question while reading a paper on RosettaCM. What does RosettaCM's superposition and thread mean? I googled it. As a result, the following results were ...
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1answer
57 views

Interaction of charged triphosphates with the ATP binding region in proteins

DNA-histone interactions involve positively charged amino acid side chains groups neutralizing the negatively charged phosphate of the sugar-phosphate backbone. Is the same true for ATP binding sites ...
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1answer
59 views

What is the thickness of the membrane if only alpha helixes are embedded of a transmembrane protien?

Given is the representation of a transmembrane protein. Calculate the thickness of the membrane if only alpha helixes are embedded in it. One turn = 5.4Å Please read: The reason I didn't submit my ...
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1answer
45 views

Using BLAST for molecular replacement in structural biology

This is my first time trying to do molecular replacement to solve a protein structure. I am using the NCBI blastp program to find suitable search models. When choosing a search model, I understand ...
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505 views

How to obtain a list of proteins sorted by the ~1400 unique protein folds?

The databases CATH and SCOP both have around 1400 unique protein folds recorded from analysis of the PDB. However, I do not see any method to access this particular data. A list of each of the 1400 ...
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1answer
653 views

What are the different types of helices in protein secondary structures and how do they differ?

What are the different types of helices in protein secondary structures and how are they differentiated? In the DSSP docs, types of helices mentioned are: Alpha-Helix, Helix-3, and Helix-5. In the ...
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How can predicting protein folding speed up drug discovery?

I'm asking this as a layperson without much knowledge in biology, so please correct me if my understanding is wrong. Recently DeepMind's AlphaFold managed to predict protein structure from acid amino ...
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Why did the protein structure prediction accuracy in terms of GDT-TS decrease from 2008 (CASP 8) to 2014 (CASP 11)?

I read on https://doi.org/10.1038/d41586-020-03348-4: Why did the protein structure prediction accuracy in terms of GDT-TS (Global Distance Test — Total Score) decrease from 2008 (CASP 8) to 2014 (...
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Why are Ramachandran angles of first and the last amino acid not necessary to define the full 3D structure of a protein chain?

I have come across an online ppt slide of the bioinformatic algorithm where it is said that first and the last amino acid Ramachandran angle is not necessary to tell all its internal coordinates. Is ...
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Generating Cartesian coordinates of each atom in protein chain from the internal coordinates using python or some software

I am trying to compute Cartesian coordinates of backbone atoms and side-chain atoms (C beta alone) for a given set of internal coordinates (bond lengths, bond angles and dihedral angles) I have ...
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142 views

Why do large, aromatic residues prefer beta-pleated sheets?

I read in many journals that amino acids with branched and large aromatic R-groups have higher beta pleated sheet propensities. However, none really go in depth into the significance or reasoning ...
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Why does sequencing virus proteins take time?

According to the below paper, the coronavirus spike protein sequence was available to scientists by end of february 2020 - the begin of march 2020 timeline. I had this question that why does ...
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Which condition is most likely to cause a buildup of materials in the lysosome?

Stated below, I must answer a question related to lysosomes. I am unsure of the answer, and have explained my reasoning after the question. Lysosomes contain hydrolytic enzymes that derive from the ...
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1answer
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Questions about Cohesin - what does the ATPase domain do, and any suggested PDBs to look at?

I've been reading about cohesin lately, and I'm confused about the head subunit interactions. I've read a few papers, and also found this nice figure from wiki that demonstrates the crux of my ...
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220 views

Protein structure prediction from amino acids sequence

Information given at this resource https://predictioncenter.org/ is close to impossible to digest (as with everything in this field), so if anyone could tell me what is the accuracy we can predict ...
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1answer
105 views

Determine similarity in percentages between species A and B, A and C, and B and C

The chart above is a graphic that shows the amino acid sequence differences between different organisms for a protein keratin. The question I am required to answer begins as, "Keratin is made up ...
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Why is protein cyclisation desirable?

There are a number of methods to "cyclize" an existing peptide: Disulphide bond as described in Disulfide Bond Mimetics: Strategies and Challenges by Gori et al. "Linchpin" based (...
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What programs account for structural alignment of different parts of distant homologs which have significant structural differences?

If there is a need to align structurally different parts of distant homologs, which program one should use? Since distant homologs often have significant structural changes, does that means the ...
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What is a Protein contact map, and how do I read one?

Protein contact maps are symmetrical and look great, but how does one read one? I tried to underside the following source: 'Understanding contact patterns of protein structures from protein contact ...
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Why are some protein sequences known but their 3D structure isn't?

Why are there some proteins that have a known amino acid sequence, but their 3D structure is not known? Wouldn't finding the former in a lab lead to the discovery of the latter? Please correct me if I ...
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1answer
56 views

Cold adaptation in proteins, at sequence & structural level

When looking for cold adaptation in unicellular eukaryotes there is not much work found. Most of the time general sequence comparative sequence analysis between marine mesophile & psychrophile ...
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Any kind of online “molecular modeling playground”?

I'm wondering if anyone has ever made a tool to try out new molecular modeling/simulation algorithms, where the tool itself handles the "boring" tasks of loading PDB files, building chains ...
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How to build SEG in your personal environment?

I'm trying to implement SEG (Wootton & Federhen,1993) in my MATLAB and Python environment. From this oriinal article I cannot figure out what I need to build my script. Are there any related ...
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125 views

Simple protein graphics software for stick models

Anybody know of a good free molecular graphics system that allows PDB file input? I prefer that it does not use Java. I also prefer that it is online, although I would consider recommended software ...
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How do you biologists draw a protein when you write a paper?

The following is one example of protein structure diagram that I want to put in my research paper. I took this from Koniev, O. & Wagner, A. “Developments and recent advancements in the field of ...
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Why does insertion of transmembrane domains occur in the rough ER?

To elaborate on that question, why in the secretory pathway does the insertion of transmembrane domains into the membrane occur in the rough ER as the protein is translated and threaded across the ER ...
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What are good techniques for determining direct maps of proteins?

I am looking for which techniques to explore to determine electron density maps (or Fourier maps) for a protein (possibly using an assumed model). In particular, I want to avoid techniques that ...
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1answer
73 views

Can the knowledge about torsion angles alone be sufficient for specifying secondary structures of protein?

I have read that Ramachandran plots are used to identify secondary structures of proteins. Also, alpha helices and beta strands cluster around specific regions of the plot which gives us the ...
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61 views

Glucose 6-phosphate dehydrogenase: reaction mechanism

I have searched the internet for the reaction mechanism of G6PD but couldn't find it, so I am asking whether anyone here knows its mechanism and whether they could recommend some sources that give ...
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851 views

Difference between prions and amyloid proteins?

Amyloid and prions are misfolded proteins, but what, if any, is the difference between them? Is amyloid a type of prion with a fibrillar structure?
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Why does the structure for cellular retinol binding protein show interactions with cadmium ions?

A structure of cellular retinol binding protein (1CRB) contains two cadmium ions as ligands. Is Cd2+ a ligand of CRBP and, if so, is that interaction necessary for protein function or is the protein a ...
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3answers
239 views

Why does it matter to predict protein structure?

And how do you predict it ? What is your input data (sequence of amino acids, temperature, pH, ...) ? Is there a "standardized" input that scientists agree on ? Moreover, I've read that knowing the ...
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1answer
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Formation of disulfide bonds in protein expressed after transduction

Say I transduce a nucleic acid sequence using a viral vector that encodes a protein having at least one disulfide linkage. For simplicity, let’s assume that there are only two cysteines in the protein ...
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Estimating diffusion constant of a protein based on number of amino acids

Is there a way to estimate the diffusion constant of a protein based on the number of amino acids it is comprised of. I know that the shape of the protein has an influence on the diffusion constant, ...
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1answer
191 views

Do all transmembrane proteins contain channels or tunnels?

In my book, there is written something like this. The integral proteins pass into the lipid bilayer to different depths and establish hydrophobic bonds with lipid molecules. Some of the integral ...
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Can 1.5 gigabytes encoded in the human genome really account for the complexity of a human being?

I read the human genome is 1.5 gigabytes in size. Thats actually not a lot; Photoshop probably takes more space. Mac OS takes 10+ gigabytes of space. Also, the genome is 1.5 gigabytes when counting ...
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What is the native structure of amyloid-beta protein under physiological conditions?

The amyloid-beta protein forms cross-beta structured fibrils. But under normal physiological conditions what is their predominant secondary structure. Is it alpha-helix, random coil or beta-sheet?
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Software to model and analyse protein–ligand interactions

I am currently trying to model a certain protein (Golgi Mannosidase II) and compare the induced fit of the inhibitor swainsonine. I would like to be able to analyse the distances between bonding ...
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Is the chitin in an insect's exoskeleton cross-linked?

This answer to the question How to clean and preserve a cicada's molted exoskeleton (exuvia)? states: The exuvia is made of cross-liked chitin, and will not decay. You don't need any special ...
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1answer
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Is α-keratin a fully functional protein?

Is α-keratin before it coils with another polypeptide, makes chains, and build intermediate filaments a fully functional protein? I mean, is the single monomer of α-keratin a protein or does it have ...
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1answer
63 views

Can denatured GFP show fluorescence?

GFP ( green fluorescent protein) can show green fluorescence. And its fluorescence is due to the tri peptide chromophore which is given in below I was wondering, can we observe fluorescence, if we ...
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62 views

Protein structure prediction using PSSM? Or not?

I have been studying protein structure prediction algorithms. A lot of recent work uses something called the PSSM, the position-specific scoring matrix. I think that what a PSSM does is to build a 2-...
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conversion of distance matrices to pdb/coordinates

I am currently facing two transformational issues. Suppose I am given a protein's residue sequence and calpha distance matrix; is there a way to generate the 3d coordinates of the protein's residues ...
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1answer
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Emergence of novel protein interactions by mutation of amino acids

Are there any examples of proteins that, without coming from a recent duplication event, underwent a mutation(s) that caused it to have a novel interaction with a new ligand, substrate, other protein ...