Tag Info

New answers tagged

3

In this paper detailed analysis has been made on spliceosome (U2-type) composition. It should be noted that this complex has dynamic composition. In the paper authors state that up to 170 proteins may associate to a metozoan spliceosome during its course of action. Individual assemblies contain approx 110 proteins (human). Similar complex of the yeast ...


2

Trp-Cage is a protein found in Gila monsters, and it is only 20 amino acids long and there are plenty of repeated amino acids so this does not use all 20. But there must be plenty of other examples, there is no reason why physically a protein must use all available amino acids.


2

As you can see on the wikipedia page you linked yourself that beta barrels have far larger diameters (in some cases up to 40 angstroms as stated in this paper) depending on the numbers of beta sheets that make up the barrel, compared to the diameter of an alpha helix (that is fixed) of 6 angstroms. (source ...


2

I'm not sure I understand the question. You've elegantly demonstrated that only a tiny fraction of all protein sequences could possibly exist, but then asked why only a tiny fraction of all protein sequences do exist. Your conclusions about independent origins of life having no proteins in common are accurate, but also consider that you as a human being have ...


11

The answer is chance or, even better, contingency. About your calculations, it is true that the theoretical sequences are almost unlimited, but the basic scaffolds are not. Very different sequences can fold into the same basic scaffold and have a similar reactivity/function. So, even if not all the sequences have been explored on this planet, most of the ...


0

PDBe's new search system is designed to answer just such questions http://www.ebi.ac.uk/pdbe/entry/search/index?organism_synonyms:HUMAN&view=macromolecules shows there are 6964 unique human macromolecules with structure data in the PDB. Of course, many will be fragments of proteins rather than the whole molecule.


5

The stacking gel concentrates proteins loaded into the sample wells so that they are resolved as a unified "line" once they enter the stacking gel. The reason for the lower pH is that this "lower ionic strength implies higher electrical resistance and consequently a higher electric field, provoking the faster movement of the proteins and of every other ...


4

The other major difference between the two is the amount of acrylamide in the upper (stacking) gel - it's generally around 4%, while the lower (resolving) gel can vary from 6 or 8% to 20%, depending on the size of the protein(s) you're looking for. When you load your samples in the wells at the top of the gel, then start the current, not all of the sample ...


5

The word complex in your sentence designate a protein complex, also called multiprotein complex. A protein complex is a group of two or more polypeptide chains that bind together to make up a functional unit. A complex can be made up of similar polypeptide chains or totally different polypeptide chains. Proteasome, Metabolon or hemoglobins are examples. ...


4

TL;DR: Chymosin is similar to pepsin and I couldn't find any evidence of functional/expressed chymosin gene in human genome. It seems like a common misconception that chymosin is functional in humans. Already in 1940s it has been shown that rennin (aka chymosin) is absent from "gastric juice" in adult humans. Genetically there is only pseudo-gene for ...


0

Might I suggest you go directly to the source? Here is a link to a paper published by Francis Crick (et al) in 1957 entitled: 'Codes Without Commas' http://www.ncbi.nlm.nih.gov/pmc/articles/PMC528468/


8

A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step ...


1

After I had check so many possibilities I finally resolve the problem. It turns out that ph of the tris 1,5M for gel preparation was too many basic...which explain a smear of the proteins into the gel



Top 50 recent answers are included