March 2024 - modeller_usage

Error identifying new atomtypes in $RADII_LIB while adding new residue into modeller topology library
by Neeraj Kumar T . 21 Mar '24

21 Mar '24

I've been trying to add a new residue's (ligand) topology and parameters into modeller library to model accurately. I am following the steps in modeller's FAQ #8: https://salilab.org/modeller/FAQ.html#8. After adding the topology into a copy of "top_heav.lib", and parameters into a copy of "par.lib", and also into copies of "radii.lib" and "solv.lib", I still get errors. This is the initial script I used: ------------------ [image: image.png] -------------------- The above script gives error in the 5th command-line as follows: ------------------------------ *ERROR Case-1:* >>> env.libs.parameters.append(file='$(LIB)/radii_edited.lib') read_pa_233E> No keyword before contents. Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python3.10/dist-packages/modeller/parameters.py", line 25, in append return _modeller.mod_parameters_read(self._modpt, self.__libs.modpt, _modeller.ModellerError: read_pa_233E> No keyword before contents. >>> ------------------------------- Therefore, I deleted command-lines 5&6, and executed the following script. ----------------------------- [image: image.png] ---------------------------------- And executing the above script gave the following error for the 5th command-line: -------------------------------------- *ERROR Case-2:* >>> env.libs.topology.read(file='$(LIB)/top_heav_edited.lib') read_to_681_> topology.submodel read from topology file: 3 read_to_231E> CHARMM atom type is not recognized (not in RADII_LIB): CG2D1O Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python3.10/dist-packages/modeller/topology.py", line 23, in read return self.append(file) File "/usr/lib/python3.10/dist-packages/modeller/topology.py", line 28, in append return _modeller.mod_topology_read(self._modpt, self.__libs.modpt, _modeller.ModellerError: read_to_231E> CHARMM atom type is not recognized (not in RADII_LIB): CG2D1O -------------------------------- This happens inspite of the fact that I have added the radii of new atomtypes into "radii.lib" file itself, and not in the copy "radii_edited.lib", as follows: [image: image.png]

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Modelling based on two templates - one oligomer and one monomer
by hmad3＠cam.ac.uk 19 Mar '24

19 Mar '24

Hello, I am trying to model a multichain protein using 2 templates - the .pdb file of an oligomer (with the same number of chains as the target) and the .pdb file of the AlphaFold structure of one of the monomers making up the target protein. (When I model using only the oligomer as target, the model of the target looks quite "off".) First scenario: * target protein: 5 of the same chain * template protein 1 ("base template"): a homopentamer * template protein 2 ("sub-template" - i.e. the target protein is first modelled based on the first template then modelled based on the 2nd template): the AF predicted structure of one chain of the target protein (the .pdb file has only one chain). Second scenario: * target protein: a heteropentamer - 2 of one chain + 3 of another chain * template protein 1: as in the previous scenario * template protein 2 (+3): AF predicted structures of the two chains making up the target heteropentamer. There are 2 AF folds, one for each monomer, each one with a single chain. How would I format the alignment file? I look forward to your guidance. Kind regards, Amanda

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Alignment to use when I am modelling a heteromer using a homer as template
by hmad3＠cam.ac.uk 18 Mar '24

18 Mar '24

Hello, I am currently modelling a heteromeric protein using a homomeric protein as a template, as follows: - heteromer subunits (target): 2 x aaaaaaaa + bbbbbbbbb - homomer subunits (template): 3 x cccccccccc When aligning the monomer sequences to be used in the .ali file, should I align aaaaaaaa and cccccccccc separately, then bbbbbbbbb and cccccccccc and use the sequences generated in the FASTA file of each alignment in the .ali file -- or should I align all three sequences at once and use the sequences in the FASTA file in the .ali file? (In the first case, there would be two FASTA files and "cccccccccc" would be aligned differently, and both alignments of cccccccccc would be used in the .ali file. In the second case, there would be one FASTA file.) I look forward to your response. Kind regards, Amanda

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I don't want to use one region of a *target* for construction of my model.
by hmad3＠cam.ac.uk 12 Mar '24

12 Mar '24

Hello, I am modelling a pentameric protein based on a template with missing residues, e.g. aaaaabbbbbdddddeeeee (except the original protein sequence has "ccccc" corresponding to a long disordered region between the "b" and "d", but this is not modelled, hence the FASTA of the protein looks like the above, and the .pdb file and 3D model of the protein would show "missing residues" between "b" and "d") The original sequence of the target protein is: fffffggggghhhhhiiiiijjjjj except "iiiii" is a disordered region which aligns with "ccccc" in the template. If I remove "iiiii" from the sequence before aligning with the above template sequence (without the disordered region), "h" and "j" will be interpreted as continuous in the .pdb file of the target generated, affecting the structure of the protein. How would I make PDB interpret a gap between "h" and "j" that aligns with the gap between "b" and "d" in the template? With thanks and kind regards, Amanda

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