Biosynthesis and disulfide cross-linking of outer membrane components during the growth cycle of Chlamydia trachomatis.

Abstract

The synthesis and accumulation of Chlamydia trachomatis outer membrane proteins within infected HeLa 229 host cells were monitored by assessing the uptake of [35S]cysteine into chlamydial proteins during the 48-h growth cycle of a lymphogranuloma venereum strain, L2/434/Bu. Synthesis of the major outer membrane protein, a protein that accounts for about 60% of the outer membrane protein mass of elementary bodies (EB), was first detected between 12 and 18 h after infection. The uptake of [35S]cysteine into the 60,000-molecular-weight doublet (60K doublet) and 12.5K cysteine-rich proteins was not observed until 30 h after infection, when the intracellularly dividing reticulate bodies were beginning to transform into infectious EBs. By using a more sensitive immunoblotting method in conjunction with monoclonal antibodies specific for the 60K doublet proteins, synthesis of these proteins was detected even earlier, by 18 h after infection. These data suggest that the time and extent of synthesis of these outer membrane proteins are regulated by processes that coincide in time with the transformation of reticulate bodies into EBs. Additional studies were performed to determine the extent of disulfide cross-linking of outer membrane proteins during the growth cycle. Both the major outer membrane protein and the 12.5K protein became progressively cross-linked to about 60% during the last 24 h of the growth cycle, whereas the 60K doublet proteins were extensively cross-linked during most of the cycle. These data may indicate an intracellular cross-linking mechanism, possibly enzymatic, that exists in addition to an auto-oxidation mechanism that occurs upon host cell lysis and exposure to the extracellular environment.