Mycobacterium smegmatis produces an HBHA homologue which is not involved in epithelial adherence.
Mycobacterium tuberculosis produces heparin-binding hemagglutinin (TB-HBHA), an adhesin involved in binding to non-professional phagocytes and in extrapulmonary dissemination. TB-HBHA binds sulphated glycoconjugates through its C-terminal lysine-rich domain and can be purified by heparin-Sepharose chromatography. Homologues of HBHA are found in other pathogenic mycobacteria, but previous investigations failed to demonstrate them in non-pathogenic Mycobacterium smegmatis. We identified a gene encoding a HBHA-like protein, named MS-HBHA, from the complete M. smegmatis genome. The deduced MS-HBHA amino acid sequence revealed 68% identity with that of TB-HBHA and contains lysine-rich repeats in its C-terminal domain. However, in contrast to TB-HBHA, the lysine-rich domain of MS-HBHA is preceded by a stretch of acidic residues. This difference likely explains the low affinity for heparin displayed by MS-HBHA compared to TB-HBHA. Isolation by heparin-Sepharose chromatography procedure and mass spectrometry analysis indicated that MS-HBHA, similar to TB-HBHA contains several methylated lysine residues in its C-terminal domain. Although MS-HBHA is associated with M. smegmatis cell wall fractions, it does not seem to play a role in epithelial adherence and its function remains unknown. We therefore conclude that TB-HBHA may have evolved as an adhesin in pathogenic mycobacteria from a homolog that serves a different function in a saprophytic mycobacterium.
Biet
Franck
F
UR1282, Infectiologie Animale, Santé Publique (IASP-311), INRA Centre de Tours, F-37380 Nouzilly France. franck.biet@tours.inra.fr
Angela de Melo Marques
Maria
M
Grayon
Maggy
M
Xavier da Silveira
Erika Kopp
EK
Brennan
Patrick J
PJ
Drobecq
Hervé
H
Raze
Dominique
D
Vidal Pessolani
Maria Cristina
MC
Locht
Camille
C
Menozzi
Franco Dante
FD
D018829:Adhesins, Bacterial / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D002458:Cell Fractionation; D002460:Cell Line; D002473:Cell Wall / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology*; D016680:Genome, Bacterial / Q000235:genetics; D006801:Humans; D037102:Lectins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D037102:Lectins; C104578:heparin-binding hemagglutinin