# Converting Amber pdb to GROMACS pdb to output a topology
**URL:** https://gromacs.bioexcel.eu/t/converting-amber-pdb-to-gromacs-pdb-to-output-a-topology/8475
**Category:** User discussions
**Created:** [February 29, 2024, 9:43pm UTC](https://gromacs.bioexcel.eu/t/converting-amber-pdb-to-gromacs-pdb-to-output-a-topology/8475 "2024-02-29T21:43:11Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@ryanm](https://gromacs.bioexcel.eu/u/ryanm)
#### Post date: [February 29, 2024, 9:43pm UTC](https://gromacs.bioexcel.eu/t/converting-amber-pdb-to-gromacs-pdb-to-output-a-topology/8475/1 "2024-02-29T21:43:11Z")
Hello,
I used GAMES and Amber to parameterize the metal ion in my enzyme. I used Acpype to convert the prmtop and inpcrd files to GROMACS gro and top files. I converted the gro file to a pdb file, and the old top file I don’t want. Now, I want to use pdb2gmx to generate a new topology file from the new pdb file, but when I run the command everything works till the code has to write out the new topology file. I get this error for Charmm forcefields:
Fatal error:
Residue ‘HIE’ not found in residue topology database
I get this error for all of the Amber forcefields:
Fatal error:
Residue ‘GU1’ not found in residue topology database
Which I know I need to convert the residue names in the new pdb file. I could do maunally, but is there a table of all of the residue conversions from AMBER (my new pdb file) to GROMACS for I can generate a new topology?
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### Author:  [@milosz.wieczor](https://gromacs.bioexcel.eu/u/milosz.wieczor)
#### Post date: [March 1, 2024, 11:28am UTC](https://gromacs.bioexcel.eu/t/converting-amber-pdb-to-gromacs-pdb-to-output-a-topology/8475/2 "2024-03-01T11:28:51Z")
Amber’s HIE is CHARMM’s HSE/HISE, you can substitute the names and it should work.
GU1 doesn’t look like any standard residue though, so I wouldn’t expect it to work out of the box.