From Bioinformatics.Org Wiki
A recent review on proteomics in the journal Nature defined the field this way:
"The term proteome was first coined to describe the set of proteins encoded by the genome1. The study of the proteome, called proteomics, now evokes not only all the proteins in any given cell, but also the set of all protein isoforms and modifications, the interactions between them, the structural description of proteins and their higher-order complexes, and for that matter almost everything 'post-genomic'."
Michael J.Dunn, the Editor-in-Chief of Proteomics defines the "proteome" as:
"the PROTEin complement of the genOME"
and proteomics to be concerned with:
"qualitative and quantitative studies of gene expression at the level of the functional proteins themselves"
"an interface between protein biochemistry and molecular biology"
Characterizing the many tens of thousands of proteins expressed in a given cell type at a given time---whether measuring their molecular weights or isoelectric points, identifying their ligands or determining their structures---involves the storage and comparison of vast numbers of data. Inevitably this requires bioinformatics. Here is a constructively skeptical review by Lukas Huber.