FtsZ (protein)

FtsZ is a protein that is important in cell reproduction, particularly bacteria. FtsZ is one of the proteins that builds the band (called a septum) that grows around some bacteria during fission and helps them replicate. The FtsZ protein builds a specific part of the bacterium septum called the Z ring. The structure of the septum is very specific, and it is built by a number of specific proteins. The FtsZ protein is just one of at least ten proteins that are common in bacteria cell reproduction. In addition, the FtsZ protein has been found in chloroplasts and helps the tiny parts of the plant cell divide.

Background

Cells are microscopic structures that are the basis for life. Two types of cells exist: prokaryotic and eukaryotic. Eukaryotic cells have a nucleus, which is a special structure that holds important information about the cells. Prokaryotic cells do not have a nucleus. Bacteria are single-celled organisms that have simple internal structures. They are prokaryotic cells. Many different types of bacteria exist, and some are helpful to humans, while others are harmful. Some bacteria help people by breaking down materials in their digestive systems. Others can be harmful by causing infections, such as pneumonia.

All bacteria replicate through binary fission, which means one cell splits itself into two cells. When one looks at bacteria replicating under a microscope, the process seems simple. For example, the replication process for Escherichia coli (E. coli) looks like this: One cell grows larger, a band forms around the middle, and then the two parts (one above the band and one below the band) split apart. Although the process looks somewhat simple, it is actually very complex. This complicated process also happens very quickly. E. coli cells can divide every twenty minutes.

The fts in FtsZ stands for "filamentous temperature sensitive." This name indicates that most of these proteins are sensitive to temperature changes. FtsZ was first identified in the 1970s when scientists were studying mutations of E. coli. Scientists noted that the mutations occurred in E. coli when it was replicated at higher temperatures. When the cells replicated at restrictive temperatures, the cells had filamentous morphology (i.e., had thin, thread-like projections). The proteins in the septum caused this mutation. Therefore, the fts proteins are those proteins that can cause cells to grow mutations at temperatures that are not ideal.

Overview

The bacterium cell replication process requires many different factors, such as specific genes and specific proteins. The genes inside the bacteria tell the cell how to reproduce. The E. coli bacterium replicates when its genes instruct its part to follow certain steps. First, the mother cell (the cell that will divide into two to reproduce) creates copies of its chromosomes. Then, the two copies move to different ends of the cell. The genes then tell the cell how to create the septum.

Specific genes in the cell indicate that the FtsZ protein is required to create the septum. In the first stages of cell division, the FtsZ protein is located throughout the cell's cytoplasm. (Cytoplasm is fluid that fills the inside of the cell.) As the cell grows in size, the FtsZ begins to travel toward the site where the septum will form. Then, the FtsZ begins to collect. The FtsZ binds together. It eventually builds a structure called the Z ring. The Z ring is one part of the septum. FtsZ is just one protein that is common in bacteria cell division. Other proteins are also important in building the septum. Genes indicate which other proteins are required to build the septum. These proteins also align and create rings that help build the septum.

As the mother cell grows, the septum also grows. Then, the septum begins to constrict the center of the cell. The septum eventually constricts entirely, creating two fully formed bacteria cells called daughter cells. Each daughter cell has all the same genetic material as the mother cell. Eventually, the two daughter cells will also replicate. This is how bacteria colonize.

Scientists have found that, at least in some bacteria cells, the location of the Z ring is guided by a protein called MapZ. The location of the Z ring is extremely important because it determines where the septum will be located. It also determines where the two daughter cells will split apart. The septum must be located directly in the middle of the mother cell so that the two daughter cells form correctly. Consequently, MapZ is also a very important part of the cell division process.

Although a number of different proteins work together to create the septum, FtsZ is unique because it functions early in the process of creating the septum. This protein must complete its job before other proteins can build their structures, which are also important to the overall septum structure. If the FtsZ protein encounters a problem, it can cause problems in cell reproduction.

FtsZ, in addition to aiding the replication of bacteria cells, also aids in the replication of chloroplasts. Chloroplasts are organelles, or cell parts, that grow in plant cells and some other cells, such as algae. Chloroplasts do not grow in animal cells. Bacteria require only one FtsZ gene for replication. However, chloroplasts often need two or more FtsZ genes to replicate. The two FtsZ genes present in chloroplasts are FtsZ1 and FtsZ2. Scientists do not fully understand the differences between FtsZ1 and FtsZ2. However, if a chloroplast is missing one of these genes, its replication process is disrupted. Bacteria and chloroplasts have a number of similarities, including the fact that they both use FtsZ to replicate. These similarities have caused scientists to theorize that chloroplasts were once primitive bacteria cells.

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