Abstract
Collagen is the most abundant protein in higher animals and as such it is a valuable source of amino acids and carbon for saprophytic bacteria. Due to its unique amino acid composition and triple-helical tertiary structure it can however only be cleaved by specialized proteases like the collagenases secreted by some bacteria. Among the best described bacterial collagenases are ColG and ColH from Clostridium histolyticum. Many Bacillus species contain homologues of clostridial collagenases, which play a role in some infections caused by B. cereus. Detailed biochemical and enzymatic characterizations of bacillial collagenases are however lacking at this time. In an effort to close this gap in knowledge we expressed ColQ1 from B. cereus strain Q1 recombinantly, investigated its metal dependency and performed peptide, gelatin and collagen degradation assays. Our results show that ColQ1 is a true collagenase, cleaving natively folded collagen six times more efficiently than ColG while at the same time being a similarly effective peptidase as ColH. In both ColQ1 and ColG the rate-limiting step in collagenolysis is the unwinding of the triple-helix. The data suggest an orchestrated multi-domain mechanism for efficient helicase activity.
Highlights
Collagen is the most abundant protein in higher animals and as such it is a valuable source of amino acids and carbon for saprophytic bacteria
The best-described bacterial collagenases are collagenolytic activity (ColG) and H from Clostridium histolyticum. They are large (≈115 kDa) multi-domain proteins consisting of an N-terminal collagenase unit (CU) which in turn is subdivided into the activator domain (AD) and the peptidase domain (PD)[8,9]
The peptidase domain of clostridial collagenases can be further divided into a helper and a catalytic subdomain, with the latter being made up of an upper and a lower half-domain[15]
Summary
Collagen is the most abundant protein in higher animals and as such it is a valuable source of amino acids and carbon for saprophytic bacteria. Our results show that ColQ1 is a true collagenase, cleaving natively folded collagen six times more efficiently than ColG while at the same time being a effective peptidase as ColH. The primary function of bacterial collagenases is the degradation of collagen as an amino acid and nitrogen source, and as such they enable the recycling of collagen within the global nitrogen cycle[17,18]. They are relevant as virulence factors in some diseases such as gas gangrene (C. perfringens)[6] or botulism (C. botuli‐ num)[6], and present interesting targets for novel a ntibiotics[19]. Collagenases isolated from C. histolyticum are in medical and biotechnological use as wound debridement agents[20], treatment for Dupuytren’s contracture[21,22], islet cell isolation[23,24,25] and in the food and leather industry[26,27]
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