mccA curation notes

• UniProt evidence: UniProt identifies Q88FM2 as a biotin carboxylase; its MCC-alpha InterPro and PANTHER assignments and liu operon context specify the physiological complex. [file:PSEPK/mccA/mccA-uniprot.txt "RecName: Full=Biotin carboxylase"].
• The target contains both the biotin-carboxylase domain and a biotin/lipoyl carrier domain with the conserved biotin attachment motif. [file:PSEPK/mccA/mccA-uniprot.txt "InterPro; IPR011764; Biotin_carboxylation_dom."] [file:PSEPK/mccA/mccA-uniprot.txt "PROSITE; PS00188; BIOTIN; 1."].
• In the characterized P. aeruginosa system, the two MCC subunits map to liuB/liuD, supporting the two-part MccA-MccB complex assignment in KT2440. PMID:16272386.
• MccA directly enables biotin carboxylase activity and biotin binding, but only contributes to the complete methylcrotonoyl-CoA carboxylase reaction performed by assembled MccA-MccB.