MoFe protein 

2 pairs of identical subunits (tetramer, nif D & nif K)

A total of MW 180 ~ 235kD

Each subunit has 2 Mo-Fe-S clusters.

Both Fe proteins and MoFe proteins are sensitive to O2. 

TLS Online TPP Program

#Id: 8324

#Section 3: Genetics, Cellular and Molecular Biology

The rate of addition of monomers is given by

rate constant kon (M–1 sec–1 )

The rate of loss is given by koff (sec–1)

TLS Online TPP Program

#Id: 8323

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 8322

#Section 3: Genetics, Cellular and Molecular Biology

Steady-state phase

G-actin monomers exchange with subunits at the filament ends, but there is no net change in the total length of filaments.

TLS Online TPP Program

#Id: 8321

#Section 3: Genetics, Cellular and Molecular Biology

Elongation phase

short oligomer rapidly increases in length by the addition of actin monomers to both of its ends, causing filament elongation

TLS Online TPP Program

#Id: 8320

#Section 3: Genetics, Cellular and Molecular Biology

The lag phase can be reduced or abolished entirely by adding premade nuclei.

TLS Online TPP Program

#Id: 8319

#Section 3: Genetics, Cellular and Molecular Biology

Nucleation phase 

Lag period (Time taken for nucleation) Rate-limiting Step.