Proteins secreted by Gram-negative cells face multiple obstacles, including . Multiple choice question. moving across the periplasmic space underlying the thick peptidoglycan layer of the cell wall moving across the plasma membrane moving across the plasma membrane and the thick peptidoglycan layer of the cell wall moving across both the plasma membrane and the outer membrane

moving across both the plasma membrane and the outer membrane

Explanation:

Gram-negative bacteria are bacteria that have a plasma membrane, a thin peptidoglycan layer, and an outer membrane (the space between the plasma membrane and the outer membrane is known as periplasm). Moreover, Gram-positive bacteria exhibit neither outer membrane nor periplasmic space and are surrounded by thick layers of peptidoglycan. Gram-negative bacteria have developed different protein secretion systems (types I–VI and type VIII) in order to secrete proteins into the extracellular space. For such purpose, the XcpQ protein (which is an outer membrane protein from the secretin family) participates in different transport processes in Gram-negative bacteria.

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