InterPro(https://www.ebi.ac.uk/interpro/) classifies the protein families and predicting domain. This allows sequences to be scanned against InterPro's signatures by several different databases.

The STRING database (https://string-db.org/) gives information using a number of functional classification systems such as GO, Pfam and KEGG, including experimental data, computational prediction methods and public text collections.

"Requiring help" may either mean that two or more proteins are required to form one functional complex or that two or more proteins have to act sequentially to achieve the desired function. Yeast two-hybrid screening ( https://en.wikipedia.org/wiki/Two-hybrid_screening ) is one of the classical methods to identify with which other proteins a given protein interacts. You can also test whether you can pull down any other proteins with your protein-of-interest and identify these by mass-spec. Sequentially acting protein pathway have been identified by collecting mutations giving similar phenotypes, but located in different genes. Many of the classical signal transduction pathways have been elucidated in Drosophila through cross-breading experiments.

However, first check the literature and protein-protein interaction databases to see whether the necessary experiments have already been done. Check the UniProt record (https://www.expasy.org) for the homolog of your protein in the closest model organism. Here is a list of some more protein-protein interaction databases: https://openwetware.org/wiki/Protein-protein_interaction_databases

You may also check the Kegg Database (https://www.kegg.jp) for pathways encompassing your protein.

Thank you Dr. Annemarie Honegger it was really helpful.

Article Discerning molecular interactions: A comprehensive review on...

You can use any interaction data from dedicated interaction databases such as STRING, GeneMania. STRING gives interactions along with the confidence scores for that particular interactions. It also provides functional enrichment of gene-sets. Hope the information is helpful..

Happy learning..