Final answer:
Proteins destined for the bacterial cell membrane are targeted by signal sequences and inserted into the membrane with the help of cellular machinery such as the SRP in eukaryotes. Bacterial proteins use a similar mechanism involving partially elongated signal peptides to guide ribosomes to the plasma membrane for protein insertion.
Step-by-step explanation:
Proteins destined for the bacterial cell membrane are targeted to the inner membrane by a signal sequence usually located at the amino terminus of the protein. This sequence guides ribosomes that are synthesizing the protein to the plasma membrane. In bacteria, proteins that assist in functions such as nutrient scavenging or cell wall synthesis are secreted into the space between the cell membrane and wall. The secretory proteins in bacteria are directed to their destinations by partially elongated signal peptides. Once at the membrane, the nascent proteins are inserted into the membrane with the help of membrane machinery.
The process involves the SRP (signal recognition particle) in eukaryotes, which functions similarly in bacteria. The SRP initially binds to the hydrophobic signal peptide and halts translation until it can find its way to the membrane. Once docked at the appropriate receptor on the membrane, the SRP detaches and the growing polypeptide is inserted into the membrane. This process may be assisted by signal peptidases that cleave the signal peptide as the protein is inserted.
Additionally, some proteins require stop transfer sequences within their amino acid sequence to insert and anchor appropriately into the membrane. This is more common in eukaryotic cells where proteins are targeted to the rough endoplasmic reticulum (RER) before transferring through the Golgi apparatus to the plasma membrane.