Making a specific door open in a dungeon with multiple doors

I've searched several different questions and can't seem to figure out my problem. I'm trying to open a specific door in a dungeon that currently has 2 doors(there will be more doors if I ever figure this out). In my PlayerController script I declared

 public DoorOpen doorOpen; //reference to my DoorOpen Class
 [SerializeField]private GameObject currentDoor; //reference to the door I'm trying to currently open

My open door script is:

  //Door check
                 RaycastHit doorHit;
                 //GameObject currentDoor;
                 Debug.DrawRay (transform.position + new Vector3(0f, 1f,0f), transform.forward * 2f, Color.red);
                 if(Physics.Raycast(transform.position + new Vector3(0f, 1f,0f), transform.forward * 2f, out doorHit)){
                     if(doorHit.collider.gameObject.tag == "Door" && Input.GetKeyDown(KeyCode.R)){
                         print ("Open the door!");
                         currentDoor = doorHit.collider.gameObject; //assigns the current door
                         doorOpen.OpenCheck (); //runs script attached to DoorOpen class
                     }
                 }

My DoorOpen class:

public class DoorOpen : MonoBehaviour { public bool isDoorOpen = false;

 public void OpenCheck(){
     if(isDoorOpen == false){
         isDoorOpen = true;
         print ("Opened");
         Vector3 to = new Vector3(0,90,0);
         transform.eulerAngles = Vector3.Lerp (transform.rotation.eulerAngles, to, Time.deltaTime * 90);
     }else{
         isDoorOpen = false;
         print ("Closed");
         Vector3 back = new Vector3 (0, -90, 0);
         transform.eulerAngles = Vector3.Lerp (-transform.rotation.eulerAngles, back, Time.deltaTime * 90);
     }
 }

}

What I'm currently getting is that in my Player Inspector window, CurrentDoor is assigning the proper door, but Door Open is remaining null. I'm thinking if I can assigned CurrentDoor to DoorOpen it should work, but when I try to do that it get "Assets/Scripts/Player/PlayerController.cs(50,17): error CS0029: Cannot implicitly convert type UnityEngine.GameObject' to DoorOpen'" If I take out the CurrentDoor step and just assign the GameObject 'door' in the player Inspector window, it will only open that specific door and not any other door.