Reviewing advancement in Mycoplasma pneumoniae P30 adhesin protein provides insights for future diagnosis and treatment

Abstract

Mycoplasma pneumoniae is a major pathogen that causes upper and lower respiratory tract infections in children, adolescents, and elderly individuals and can lead to pneumonia, intrapulmonary and extrapulmonary complications, and respiratory sequelae. M. pneumoniae must adhere to respiratory epithelial cells of a host for infection. The P1 and P30 proteins, as two adhesin proteins of M. pneumoniae, have attracted extensive attention from many researchers. In this paper, we present the latest research progress on the P30 protein in terms of structure and mutation typing, physiological function, clinical serological diagnosis and vaccine development in a literature review. This study deepens our knowledge on the pathogenesis of M. pneumoniae and is useful for diagnosing and preventing M. pneumoniae infection.

Keywords: Mycoplasma pneumoniae; P30 protein; adhesion; diagnosis; vaccine.

Figure 1

Schematic diagram of P30 protein structure. From left to right, the brackets above indicate the predicted signal peptide (SP) (yellow area), intracellular (green area), transmembrane (TM) (cyan area), and extracellular regions (remaining area) of P30. Domains I, II, and III are represented by the black horizontal lines below. Vertical black and grey bars within domain III correspond to P-rich repeat motifs PGMAPR (black), PGMPPH (light grey) and PGEPPQ (dark grey).

Figure 2

Prediction of secondary structure of P30 protein. Predictions suggest that the secondary structure of the P30 protein is dominated by alpha helices and random coiling.

Figure 3

Prediction of tertiary structure of P30 protein. This suggests that the P30 protein is a twice-transmembrane protein.

Figure 4

Schematic diagram of P30 protein function. (A) A folded conformation is formed; the P1, B and C proteins form an adhesion complex, recognize receptors on host cells and bind to host cells. (B) Mutation or deletion of P30 protein results in the transformation of M. pneumoniae into oval or multidivision cells. (C) The role of P30 protein in the gliding mechanism may be similar to that of Gli349, an adhesion protein of M. mobilis, which has a tip structure similar to “foot,” binds to host cell surface receptors and directly drives the mycoplasma to slide on the surface.Similarly, the P30 protein may play a role in Gli521, driving the P1 adhesin that may have a Gli349 function. (D) There are interactions between P30, the P1, P65 and HMW3 proteins (Figure by figdraw).

Figure 5

Structure of the M. pneumoniae major adhesion proteins and accessory proteins. M. pneumoniae adhesion proteins include major adhesion proteins the P1, P30, P116 and P65 proteins, as well as auxiliary proteins P40 and P90 (protein B and C) and high molecular weight protein HMW1-3. Together, these components form a characteristic high electron-density “adhesive protein complex” (Figure by figdraw).

Figure 6

Residues with scores above the threshold (indicated in yellow in the figure) are predicted to be part of the epitope. (A) Beta-turn prediction result; (B) Surface accessibility prediction result; (C) Flexibility prediction result; (D) Antigenicity prediction result; (E) Hydrophilicity prediction result; (F) Bepipred linear epitope prediction 2.0 result.