Microbial cell membrane proteins and enzymes containing accessible cysteine thiol groups

Microbial cell membrane proteins and enzymes containing accessible cysteine thiol groups represent a broad category of molecular targets for various antimicrobial agents, particularly heavy metals and oxidizing antiseptics (StatPearls). These targets include essential enzymes involved in metabolism and membrane-bound transporters required for nutrient uptake (PubMed). The sulfhydryl (-SH) group of the cysteine residue is highly reactive and serves as a site for covalent binding by metal ions like silver (Ag+) and mercury (Hg2+), or for oxidation by agents like iodine (PubChem). This binding results in the formation of mercaptides, which causes protein misfolding, inactivation of catalytic sites, and disruption of the microbial cell membrane's integrity. Because these thiol groups are also present in human proteins, drugs targeting this class often exhibit significant host toxicity, limiting their systemic use (NIH). Today, these interactions are primarily exploited in topical disinfectants, wound care products, and as preservatives in multi-dose vaccine vials to prevent microbial contamination.

Other names

Sulfhydryl-containing microbial proteinsThiol-containing microbial enzymesCysteine-rich microbial membrane proteinsMicrobial sulfhydryl groups

The primary mechanism involves the covalent binding of the drug (often a heavy metal ion or electrophile) to the nucleophilic sulfhydryl (-SH) groups of cysteine residues within microbial proteins. This interaction leads to the formation of stable mercaptides or disulfide bridges, which inactivates essential enzymes such as glyceraldehyde-3-phosphate dehydrogenase, disrupts membrane-bound transport systems, and compromises the structural integrity of the microbial cell wall and membrane (StatPearls, PubChem). Additionally, the modification of these proteins disrupts ion gradients and electron transport, resulting in a rapid loss of cellular homeostasis and microbial cell death (PubMed).