Question: For my undergraduate research I'm looking for a database that gives the bound form of a particular protein structure. Is there any database that provide us with such data? So far I've found following proteins related to my work 

* Ascorbate peroxidase (APX)
* Beta-glucosidase
* Calcineurin b-like protein-interacting protein kinase.

I've searched in PDB and UNIPROT.

Answer: 
Tried looking for an explicit database? i.e.

* ComSin: database of protein structures in bound (complex) and unbound (single) states in relation to their intrinsic disorder: <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808974/> or
* LigASite: a database of biologically relevant binding sites in proteins with known apo-structures <https://www.ncbi.nlm.nih.gov/pubmed/17933762>

Else the PDB itself has a very powerful advanced search that should allow you to do this: <http://www.rcsb.org/pdb/search/advSearch.do>
Are you aware of [BRENDA](http://www.brenda-enzymes.org/index.php)? I was just introduced to it today for a completely separate reason (looking at carbohydrate enzyme families in the *Nippostrongylus brasiliensis* proteome), and it seems to be a fairly comprehensive database. There is at least a literature link there for the [ascorbate-complexed crystalisation of Ascorbate peroxidase](http://www.brenda-enzymes.org/enzyme.php?ecno=1.11.1.11#Crystallization/COMMENTARY) on that site. Following through the paper, I see that [the complex has been uploaded to PDB](http://www.rcsb.org/pdb/explore/explore.do?pdbId=1OAF).