# Using CPORT to predict active and passive residues of homodimers

**URL:** <https://ask.bioexcel.eu/t/using-cport-to-predict-active-and-passive-residues-of-homodimers/366>\
**Category:** HADDOCK\
**Created:** [May 19, 2017, 7:36pm UTC](https://ask.bioexcel.eu/t/using-cport-to-predict-active-and-passive-residues-of-homodimers/366 "2017-05-19T19:36:19Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![samaneh](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@samaneh](https://ask.bioexcel.eu/u/samaneh)\
**Post date:** [May 19, 2017, 7:36pm UTC](https://ask.bioexcel.eu/t/using-cport-to-predict-active-and-passive-residues-of-homodimers/366/1 "2017-05-19T19:36:19Z")

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Dear haddock users  
I Have a PDB file of a homodimer with overlapping numbers, each chain (A and B) from 18 to 117. I sent it to CPORT and got an error about overlapping residues. I changed the residue number of Chain B to 118-227 and also removed the waters molecule with notpad++.  
My question is: "is it necessary to change chainID in my PDB? I mean B to A as if it is a monomer? and what if I only send one chain of protein to CPORT but take the result for my whole PDB ( as it is a homodimer)?  
Thank you

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**Author:** ![amjjbonvin](https://dub1.discourse-cdn.com/flex013/user_avatar/ask.bioexcel.eu/amjjbonvin/32/23_2.png) [@amjjbonvin](https://ask.bioexcel.eu/u/amjjbonvin)\
**Post date:** [May 21, 2017, 2:49pm UTC](https://ask.bioexcel.eu/t/using-cport-to-predict-active-and-passive-residues-of-homodimers/366/2 "2017-05-21T14:49:54Z")

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You can easily change chain IDs using our PDB-Tools suite of python scripts. Check

> **[haddocking/pdb-tools](https://github.com/haddocking/pdb-tools)**
>
> A dependency-free cross-platform swiss army knife for PDB files. - haddocking/pdb-tools

Can be that CPORT will work fine without changing the ChainID

As for you second question, running the monomer, might results in predictions for the dimer interface… I would rather run the dimer.

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**Author:** ![samaneh](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@samaneh](https://ask.bioexcel.eu/u/samaneh)\
**Post date:** [May 22, 2017, 5:30am UTC](https://ask.bioexcel.eu/t/using-cport-to-predict-active-and-passive-residues-of-homodimers/366/3 "2017-05-22T05:30:52Z")

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It was really helpful. Thank you.