Protein found mostly on the matrix side of the membrane.
The subcellular locations in which a protein is found are described in UniProtKB entries with a controlled vocabulary, which includes also membrane topology and orientation terms.
By default, searching the subcellular locations will look for matches in both name and definition. Example queries to search subcellular locations only by name:
Information about the usage of this controlled vocabulary in UniProtKB entries can be found in the user manual.