The 16-kDa α-crystallin (Acr) protein ofMycobacterium tuberculosisis required for growth in macrophages

Abstract

Although the 16-kDa ␣-crystallin homologue of Mycobacterium tuberculosis (MTB) is the dominant protein produced by stationary phase cultures in vitro, it is undetectable in logarithmically growing cultures. By growing bacilli at defined oxygen concentrations, acr transcription was shown to be strongly induced by mildly hypoxic conditions. Acr expression also was found to be induced during the course of in vitro infection of macrophages. The acr gene was replaced with a hygromycin resistance cassette by allelic exchange in MTB H37Rv. The resulting ⌬acr::hpt strain was shown to be equivalent to wild-type H37Rv in in vitro growth rate and infectivity but was significantly impaired for growth in both mouse bone marrow derived macrophages and THP-1 cells. In addition to its proposed role in maintenance of long-term viability during latent, asymptomatic infections, these results establish a role for the Acr protein in replication during initial MTB infection.

Improving the characteristics of a mycobacterial 16 kDa-specific chicken scFv

“…Chicken scFvs with a 15 amino acid linker (Gly 4 Ser) 3 have been found to occur mostly as monomers and a mixture of lesser amounts of multimers. Shortening the linker of the weak 16 kDa mycobacterial binder significantly improved its signal in ELISA owing to the formation of tetrameric "multibodies".…”

Mtb32 is a promising tuberculosis antigen for DNA vaccination in pre- and post-exposure mouse models

“…The majority of TB antigens have been tested or screened in various prophylactic settings, whereas a relatively small number have been studied in therapeutic models. [4][5][6] Ag85A, 7 PstS3, 8 MPT64, 9 ACR, 10,11 Mtb39,12 Mtb72F (a fusion protein of Mtb32 and Mtb39) 13 and TB10.4 (ref. 14) were examined in this study.…”

Expression of Alpha Crystallin Protein in Osteoarticular Tuberculosis in Latent Phase: A Review of Evidences

“…dosR upregulation is required for M. tuberculosis to survive within macrophages [23]. However, the 16-kDa alpha-crystallin homologue of M. tuberculosis is the dominant protein produced by stationary phase cultures in vitro, it is unnoticeable in exponentially growing cultures [17]. Hypoxia is one factor frequently associated with the establishment and maintenance of latent TB [24].…”

“…Among these genes hspX(acr, Rv2031c) is most dramatically activated (~80 folds) [17]. This hspX gene (acr) in M. tuberculosis encodes a 16kilodalton alpha-crystallinlike protein which is abundantly present in the bacterial cell wall [22].…”

“…The dosR gene responses to hypoxic and nitric oxide stresses are associates with M. tuberculosis dormancy [15] and others have demonstrated that acr protein expression was strongly upregulated in M. tuberculosis on entry into and remains at a high level during latent phase. This indicates that acris implicated in M. tuberculosis persistence or latent phase [16,17]. In the present review, the function of alpha crystallin protein is highlighted and suggesting it as a diagnostic marker for the latent infection of M. tuberculosis in osteoarticular tuberculosis.…”