You can limit your search result at NCBI by specifying the database field you want to search, for example: cytochrome B AND arabidopsis[orgn] only returns hits in the organism Arabidopsis. You will find more on the syntax of NCBI entrez queries here. In GenBank entry for CAA47966.1, on the right hand side you will find a link to CDD (Conserved Domain Database) search results. This link provides a handy graphical interface where you can easily see if any position in the protein is assigned to a specific function.